A primer on backup battery systems for power outages

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LadyGeek
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

I haven't seen any discussions about overcurrent protection. Anything that's designated as prime power needs a circuit breaker (or another way) to cutout when a surge is detected.

Surges, a large inrush current of short duration, can be substantial when starting a motor, e.g. sump pump, freezer, or refrigerator.

Be sure your inverter can accommodate inrush current. I see products which mention running wattage specs. Be sure you account for the starting wattage.
Wiki To some, the glass is half full. To others, the glass is half empty. To an engineer, it's twice the size it needs to be.
go_mets
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Re: A primer on backup battery systems for power outages

Post by go_mets »

smitcat wrote: Wed Aug 19, 2020 9:23 am
go_mets wrote: Wed Aug 19, 2020 9:13 am
smitcat wrote: Wed Aug 19, 2020 8:48 am
go_mets wrote: Wed Aug 19, 2020 8:19 am Thank you for the primer.

Given that a 100Ah lead acid battery weights 65-70 pounds,
Will a 50Ah one be enough to peridocially run a full-size side-by-side refrigerator for 2-3 days?
These are about 45 pounds.
I am looking at the ones sold by Advance Auto Parts who have a store nearby:
https://shop.advanceautoparts.com/web/S ... E_LOW_HIGH
If you want to support any full sized refrigerator and open the door from time to time over 3 days batteries will not suit your goal without a robust charging system for the batteries. By the time you add the charging system(s) (solar, small genset, wind) required you might as well get a suitably sized small generator.
Have you tried this yourself?

My calculations:
My refrigerator says it is 11.5A which I am guessing is the average current draw per hour.
So if I run 1 hour per day and the battery is 50Ah.
It would seem I would get 4 days out it.
My main goal is to not have the food spoil so I would try to avoid opening the door.
.
"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
smitcat
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Re: A primer on backup battery systems for power outages

Post by smitcat »

go_mets wrote: Wed Aug 19, 2020 9:34 am
smitcat wrote: Wed Aug 19, 2020 9:23 am
go_mets wrote: Wed Aug 19, 2020 9:13 am
smitcat wrote: Wed Aug 19, 2020 8:48 am
go_mets wrote: Wed Aug 19, 2020 8:19 am Thank you for the primer.

Given that a 100Ah lead acid battery weights 65-70 pounds,
Will a 50Ah one be enough to peridocially run a full-size side-by-side refrigerator for 2-3 days?
These are about 45 pounds.
I am looking at the ones sold by Advance Auto Parts who have a store nearby:
https://shop.advanceautoparts.com/web/S ... E_LOW_HIGH
If you want to support any full sized refrigerator and open the door from time to time over 3 days batteries will not suit your goal without a robust charging system for the batteries. By the time you add the charging system(s) (solar, small genset, wind) required you might as well get a suitably sized small generator.
Have you tried this yourself?

My calculations:
My refrigerator says it is 11.5A which I am guessing is the average current draw per hour.
So if I run 1 hour per day and the battery is 50Ah.
It would seem I would get 4 days out it.
My main goal is to not have the food spoil so I would try to avoid opening the door.
.
"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
"Others here are suggesting a few minutes in the morning and a few minutes in the evening."
What are you accomplishing then?

What we did was to adjust the cold setting in the unit 'warmer' to a point where it still met the food managers course minimums for storage temps.
Then the refrigerator would run as necessary to maintain that temperature.

I am not sure why any of this help you in any way ...
- you do not know what the load draw is on your refrigerator , use a kilowatt they are cheap and helpfull we have a few
- our kilowatts give the average use in watts over time as well, leave it on for at least one day and get the usage number
- if you have an auto defrosting unit and you cannot trun that off you have additional problems
go_mets
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Re: A primer on backup battery systems for power outages

Post by go_mets »

smitcat wrote: Wed Aug 19, 2020 9:46 am
go_mets wrote: Wed Aug 19, 2020 9:34 am
smitcat wrote: Wed Aug 19, 2020 9:23 am
go_mets wrote: Wed Aug 19, 2020 9:13 am
smitcat wrote: Wed Aug 19, 2020 8:48 am

If you want to support any full sized refrigerator and open the door from time to time over 3 days batteries will not suit your goal without a robust charging system for the batteries. By the time you add the charging system(s) (solar, small genset, wind) required you might as well get a suitably sized small generator.
Have you tried this yourself?

My calculations:
My refrigerator says it is 11.5A which I am guessing is the average current draw per hour.
So if I run 1 hour per day and the battery is 50Ah.
It would seem I would get 4 days out it.
My main goal is to not have the food spoil so I would try to avoid opening the door.
.
"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
"Others here are suggesting a few minutes in the morning and a few minutes in the evening."
What are you accomplishing then?
Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread.

.
smitcat
Posts: 6660
Joined: Mon Nov 07, 2016 10:51 am

Re: A primer on backup battery systems for power outages

Post by smitcat »

go_mets wrote: Wed Aug 19, 2020 9:48 am
smitcat wrote: Wed Aug 19, 2020 9:46 am
go_mets wrote: Wed Aug 19, 2020 9:34 am
smitcat wrote: Wed Aug 19, 2020 9:23 am
go_mets wrote: Wed Aug 19, 2020 9:13 am

Have you tried this yourself?

My calculations:
My refrigerator says it is 11.5A which I am guessing is the average current draw per hour.
So if I run 1 hour per day and the battery is 50Ah.
It would seem I would get 4 days out it.
My main goal is to not have the food spoil so I would try to avoid opening the door.
.
"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
"Others here are suggesting a few minutes in the morning and a few minutes in the evening."
What are you accomplishing then?
Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread.

.
"Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread."

I do not have to challenge anyone I was attempting to help you with accurate information.
If you have a thermomter in a refrigerator and run it for 'a few minutes' the temperture does not change much at all.
We know this from our refrigerators at work which have thermometers on the outside reading inside.

You asked these real world questions (below)and you got our best real world answers - please consider visiting a boating or RV site if you want other more detailed responses on supporting a full sized refreigerator on common lead acid batteries.

"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

go_mets wrote: Wed Aug 19, 2020 8:13 am
willthrill81 wrote: Tue Aug 18, 2020 9:26 pm You could heat an apartment surprisingly well with a small propane heater like a Mr. Buddy. We have several of the 20 lb. (i.e. the kind used with grills) tanks in reserve just in case we need to heat at least one bedroom in the house for a couple of weeks.
I got hammered on another message board by an EMT for suggesting using a Mr. Buddy.
For the record I do have a Mr. Buddy.
The EMT wrote about all the people he had to haul to the hospital from CO poisoning.
I should have also said that any time you have a flame indoors, you need a carbon monoxide detector. We have combined smoke/CO detectors in our home and our garage.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
go_mets
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Re: A primer on backup battery systems for power outages

Post by go_mets »

smitcat wrote: Wed Aug 19, 2020 9:57 am
go_mets wrote: Wed Aug 19, 2020 9:48 am
smitcat wrote: Wed Aug 19, 2020 9:46 am
go_mets wrote: Wed Aug 19, 2020 9:34 am
smitcat wrote: Wed Aug 19, 2020 9:23 am

"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
"Others here are suggesting a few minutes in the morning and a few minutes in the evening."
What are you accomplishing then?
Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread.

.
"Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread."

I do not have to challenge anyone I was attempting to help you with accurate information.
If you have a thermomter in a refrigerator and run it for 'a few minutes' the temperture does not change much at all.
We know this from our refrigerators at work which have thermometers on the outside reading inside.

You asked these real world questions (below)and you got our best real world answers - please consider visiting a boating or RV site if you want other more detailed responses on supporting a full sized refreigerator on common lead acid batteries.

"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
Thanks for the suggestion.

The real-world experience of the Bogleheads posts is a good starting point.

.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

LadyGeek wrote: Wed Aug 19, 2020 9:26 am I haven't seen any discussions about overcurrent protection. Anything that's designated as prime power needs a circuit breaker (or another way) to cutout when a surge is detected.

Surges, a large inrush current of short duration, can be substantial when starting a motor, e.g. sump pump, freezer, or refrigerator.

Be sure your inverter can accommodate inrush current. I see products which mention running wattage specs. Be sure you account for the starting wattage.
Every inverter I've ever seen has either a built-in fuse or breaker and will shut down when too large of a load is placed on it. The cables included by the manufacturer to connect the inverter to the battery are usually adequate, but they must be secured properly. If they have ring eyelets, they must be attached very firmly with washers and preferably bolts, but wingnuts might be adequate.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
go_mets
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Re: A primer on backup battery systems for power outages

Post by go_mets »

willthrill81 wrote: Wed Aug 19, 2020 9:58 am
go_mets wrote: Wed Aug 19, 2020 8:13 am
willthrill81 wrote: Tue Aug 18, 2020 9:26 pm You could heat an apartment surprisingly well with a small propane heater like a Mr. Buddy. We have several of the 20 lb. (i.e. the kind used with grills) tanks in reserve just in case we need to heat at least one bedroom in the house for a couple of weeks.
I got hammered on another message board by an EMT for suggesting using a Mr. Buddy.
For the record I do have a Mr. Buddy.
The EMT wrote about all the people he had to haul to the hospital from CO poisoning.
I should have also said that any time you have a flame indoors, you need a carbon monoxide detector. We have combined smoke/CO detectors in our home and our garage.
I completely agree with you about the CO detector.
When I was living in an apartment even though there was one provided by the landlord, I bought my own as a backup.

.
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willthrill81
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

go_mets wrote: Wed Aug 19, 2020 9:48 am
smitcat wrote: Wed Aug 19, 2020 9:46 am
go_mets wrote: Wed Aug 19, 2020 9:34 am
smitcat wrote: Wed Aug 19, 2020 9:23 am
go_mets wrote: Wed Aug 19, 2020 9:13 am

Have you tried this yourself?

My calculations:
My refrigerator says it is 11.5A which I am guessing is the average current draw per hour.
So if I run 1 hour per day and the battery is 50Ah.
It would seem I would get 4 days out it.
My main goal is to not have the food spoil so I would try to avoid opening the door.
.
"Have you tried this yourself?"
Very common on boats where there are larger battery banks and very good inverter/chargers with battery condition monitors.
Less common on RV's where weight becomes more important than on boats where extra weight is more easily supported for larger battery banks.
You can visit boating and RV sites that speak about these issues and get much greater details is you like.

Your calculations are not real world - the run hours will be higher and any need to access the refer will add loads. Ambient air temps outside the unit will affect run time as well.
We had a 14 cubic foot top and bottom refrigerator/freezers in boats in the past and they were 120 and 12 volt driven which made the battery power a bit more efficient. With much larger batteries we could not go for 3 days without the generator or shore power.

When you plug a kilowatt into the refrigerator what does it say when it is running?
I haven't bought a Kill-a-watt yet.

It sounds like you ran your refrigerator 24/7 ?
Others here are suggesting a few minutes in the morning and a few minutes in the evening.

.
"Others here are suggesting a few minutes in the morning and a few minutes in the evening."
What are you accomplishing then?
Apparently, it kept their food okay which is my goal.
You'll have to challenge them as to the veracity. Their posts are in the whole-house generator thread.
I never said "a few minutes" in that thread. I said that you should run the refrigerator for 1-2 hours in the morning and again in the evening, and you might have to run it in the early afternoon as well.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

smitcat wrote: Wed Aug 19, 2020 8:48 am
go_mets wrote: Wed Aug 19, 2020 8:19 am Thank you for the primer.

Given that a 100Ah lead acid battery weights 65-70 pounds,
Will a 50Ah one be enough to peridocially run a full-size side-by-side refrigerator for 2-3 days?
These are about 45 pounds.
I am looking at the ones sold by Advance Auto Parts who have a store nearby:
https://shop.advanceautoparts.com/web/S ... E_LOW_HIGH
If you want to support any full sized refrigerator and open the door from time to time over 3 days batteries will not suit your goal without a robust charging system for the batteries. By the time you add the charging system(s) (solar, small genset, wind) required you might as well get a suitably sized small generator.
Right. In the OP, I addressed the difficulties in running a regular residential refrigerator from a battery system. A marine battery wouldn't last more than about half a day and quite possibly only a few hours running a refrigerator. Batteries are not a panacea.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
Wiki To some, the glass is half full. To others, the glass is half empty. To an engineer, it's twice the size it needs to be.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

LadyGeek wrote: Wed Aug 19, 2020 10:20 am I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
I've never heard of that rule of thumb. According to the FDA, "A full freezer will keep the temperature for approximately 48 hours (24 hours if it is half full) if the door remains closed."

However, I totally agree that food that is thawed should be cooked and consumed or thrown away.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

It was based on anecdotal evidence - How long I could keep fish frozen in a cooler packed with ice. I was driving home from a fishing vacation and that's how long the fishing lodge owners said it would last. I figured they knew what they were talking about, as my fish survived an 11 hour drive. (I used to do this many years ago.)

It's a conservative estimate, but I've also heard from at least one neighbor that they had to throw away all their food because they lost power for a day.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

LadyGeek wrote: Wed Aug 19, 2020 10:33 am It was based on anecdotal evidence - How long I could keep fish frozen in a cooler packed with ice. I was driving home from a fishing vacation and that's how long the fishing lodge owners said it would last. I figured they knew what they were talking about, as my fish survived an 11 hour drive. (I used to do this many years ago.)

It's a conservative estimate, but I've also heard from at least one neighbor that they had to throw away all their food because they lost power for a day.
Keep in mind that a cooler packed with ice isn't going to be nearly as cold as a freezer, which is normally kept at around 0 F. A freezer packed with ice is generally going to have an internal temperature between 30-40 F. Also, freezers are usually insulated better than coolers. But yes, if a freezer does not have much in it, which serves as a sort of internal 'thermal battery', and the ambient temperature around the freezer is high, it can certainly thaw in a day. For this reason, if you don't have much in a freezer, it's a good idea to freezer water bottles or jugs inside it to help it retain its temperature in the event of a power loss.

It's a good idea to throw blankets, sleeping bags, quilts, etc. over a refrigerator or freezer that is not running in order to add to the insulation they already have. This should be removed when the compressor is running in these units though, because the compressor needs to move the heat from inside it to the outside. In the past, refrigerators and freezers had exposed coils for this purpose, but these are now usually built in to one side of the unit. Unless you know which side that is, it's best to remove all of that insulating material when the compressor is running.
Last edited by willthrill81 on Wed Aug 19, 2020 10:42 am, edited 1 time in total.
“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” J.R.R. Tolkien,The Lord of the Rings
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Re: A primer on backup battery systems for power outages

Post by smitcat »

LadyGeek wrote: Wed Aug 19, 2020 10:20 am I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
Yes , exactly. For those that have taken the Food course (DOH) to be a licensed food server they will show you how temps go up faster than most would think and the problems that can and will occurr with food that is not kept completely refrigerated or frozen.
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Re: A primer on backup battery systems for power outages

Post by smitcat »

willthrill81 wrote: Wed Aug 19, 2020 10:07 am
smitcat wrote: Wed Aug 19, 2020 8:48 am
go_mets wrote: Wed Aug 19, 2020 8:19 am Thank you for the primer.

Given that a 100Ah lead acid battery weights 65-70 pounds,
Will a 50Ah one be enough to peridocially run a full-size side-by-side refrigerator for 2-3 days?
These are about 45 pounds.
I am looking at the ones sold by Advance Auto Parts who have a store nearby:
https://shop.advanceautoparts.com/web/S ... E_LOW_HIGH
If you want to support any full sized refrigerator and open the door from time to time over 3 days batteries will not suit your goal without a robust charging system for the batteries. By the time you add the charging system(s) (solar, small genset, wind) required you might as well get a suitably sized small generator.
Right. In the OP, I addressed the difficulties in running a regular residential refrigerator from a battery system. A marine battery wouldn't last more than about half a day and quite possibly only a few hours running a refrigerator. Batteries are not a panacea.
"A marine battery wouldn't last more than about half a day and quite possibly only a few hours running a refrigerator."
Agreed - while you can get much better details on this at boating and RV sites this article has a summary that may be useful:

https://homeguides.sfgate.com/run-refri ... 49672.html

"Lead-acid rechargeable batteries are rated in ampere-hours. A typical battery rated at 105 ampere hours can deliver 105 DC amps for one hour before it runs out of power. In general, you risk damage if a rechargeable lead-acid battery is drained below 50 percent of capacity, so you safely can draw 105 amps for only 30 minutes. A fridge drawing only 55 DC amps can be run for about 60 minutes of continuous duty off a 105 ampere-hour battery. Refrigerators run intermittently, not continuously, so you need to determine how many minutes out of each hour your refrigerator actually runs. If your refrigerator draws 55 DC amps for 20 minutes out of each hour, you will need to recharge your battery after three hours of refrigerator operation. A second battery will keep your fridge running while you recharge the first battery."
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Re: A primer on backup battery systems for power outages

Post by tyrion »

This was a very interesting read, thanks for putting it together Will.

I'm reminded of 10ish years back when I was considering building an electric bike. The parts were all there - motors, batteries, controllers, etc - but it required quite a bit of knowledge to do it yourself. You had to buy the right wheel to fit your frame, and decide between geared or direct drive, and you could overpower it to exceed the legal speed limit (depending on state) or over-battery it for great range. DIY had performance advantages and big price advantages over buying a ready-to-ride ebike. But you had to know what you were doing, and there were maintenance/charging issues so you had to be on top of things to keep it running.

In the end I decided it wasn't worth the hassle. Mostly because it seemed like it was getting less safe to ride a bike on the road as drivers were getting more distracted. But partly because it seemed like waiting a few years might yield better mainstream results.

It seems like the Li-Ion battery packs like the ones linked earlier (jackery, etc) are the equivalent of mainstream e-bikes. They just work. You don't need to know all the ins and outs, just plug it in to use it, keep an eye on the gauge, use a generator (or solar panels) to recharge it as necessary. Ideal to pair with a generator. Pricer than doing it yourself, but with advantages in simplicity.

Personally, I am getting Tesla PowerWalls installed in a few months. Combined with solar and in a very sunny location it should keep us running in almost all scenarios. The 2 batteries will hold almost a days worth of standard energy for us (assuming limited AC). If we strip away the stuff we would turn off in a grid outage (pool pump, hot tub, oven, etc) it would be closer to 2-3 days.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

tyrion wrote: Wed Aug 19, 2020 11:39 amIt seems like the Li-Ion battery packs like the ones linked earlier (jackery, etc) are the equivalent of mainstream e-bikes. They just work. You don't need to know all the ins and outs, just plug it in to use it, keep an eye on the gauge, use a generator (or solar panels) to recharge it as necessary. Ideal to pair with a generator. Pricer than doing it yourself, but with advantages in simplicity.
That's a good point. Lithium-ion batteries are certainly a lot easier to maintain that lead acid batteries and more user friendly, though they are still much pricier for their power output than lead acid batteries. Those who gravitate toward the pre-made battery packs are probably not too interested in this topic, but I suspect that many of those who own portable generators might.

For myself, a fairly simple understanding of electricity and basic electrical components has served me very well.
tyrion wrote: Wed Aug 19, 2020 11:39 amPersonally, I am getting Tesla PowerWalls installed in a few months. Combined with solar and in a very sunny location it should keep us running in almost all scenarios. The 2 batteries will hold almost a days worth of standard energy for us (assuming limited AC). If we strip away the stuff we would turn off in a grid outage (pool pump, hot tub, oven, etc) it would be closer to 2-3 days.
Good for you. Reducing one's dependence on the electrical grid is wise, especially when it makes good financial sense.
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Re: A primer on backup battery systems for power outages

Post by silverlitegs »

This is an interesting topic. This past weekend I was looking for plans to setup a temporary system of solar panels and batteries to serve a fridge ,freezer and random electronics during an extended outage . Figuring the draw would be 2k Watts a day. I haven’t been able to find a definitive article.
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Re: A primer on backup battery systems for power outages

Post by whomever »

"It seems like the Li-Ion battery packs like the ones linked earlier (jackery, etc) are the equivalent of mainstream e-bikes. They just work. You don't need to know all the ins and outs, just plug it in to use it, keep an eye on the gauge, use a generator (or solar panels) to recharge it as necessary. Ideal to pair with a generator. "

One caveat about 'pair with a generator'. Ideally, I would think you would want the generator to be able to charge at high rates (so the generator doesn't have to run a long time). Some of the 'solar generators' don't allow high charge rates. For example, my Jackery 240 uses a common input jack for charging via solar panels or 12V (from a car or generator). It does that, I think, because if it tried to draw too much current from a car cigarette lighter port it could blow the car's fuse. The upshot is that is takes several hours to charge no matter how many panels or what kind of generator you connect it to.

There are others that have higher limits (by having separate input jacks for car charging and solar panels or other 12V source). In any event, this is something you want to check.

Another point on cost: AFAIK, the batteries in the Jackery et al aren't intended to be replaceable, so when the batteries reach end of life you get to throw away the inverter and so on as well. With a DIY with discrete parts, you just buy a new battery. The jackery, IMHO, is great for a portable, but I think I would lean towards building one for a stationary application.
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Re: A primer on backup battery systems for power outages

Post by Miriam2 »

linuxizer wrote: UPSs come in different classes. Once you’re past the cheapie consumer models, you can get 220v systems, rackmount systems, double conversion, extended run, etc.
Are these 2 considered the cheapie consumer models? :wink:

https://www.apc.com/shop/us/en/products ... V/P-BN4001 - I have this
https://www.apc.com/shop/us/en/products ... /P-SMT750C - my son has this
000 wrote: Tue Aug 18, 2020 9:25 pm I've often wondered how I would know to "save my work and shutdown the computer" if I was temporarily away from it. Does the UPS emit some kind of alert? How have you approached this?
Yes, this is a key Q. How do we protect our desktops that are on when we are away from our house and our electricity goes off for a hour or so? We need a UPS that supplies battery power to our computer for hours, like my home security system does for my alarm.
willthrill81 wrote: Tue Aug 18, 2020 9:28 pm When you lose power, you generally know it if you're in the house because the lights go out and everything suddenly stops. But yes, every UPS I've seen starts making a very annoying beeping sound when power is lost to let you know that you need to shut down the system. Most only give you around ten minutes or so of power.
LadyGeek wrote: Tue Aug 18, 2020 7:35 pm For a computer battery backup system, I size my UPS for the amount of time I need to save my work and shutdown the computer. About 5 minutes of run time for the PC and monitor is all I need. My printer is not on the UPS.

Once I shutdown my PCs (I have 2 PCs and 2 UPSs), I'll bring my generator online and switch to my laptop to save power.

The UPS is also helpful when the power coming into the house intermittently drops a phase - which can happen during a storm.
Willthrill and LadyGeek - we are not always home to hear the UPS beeps when our computer is on and the power goes out. Don't these UPSs supply backup power for an hour or two or more, keeping the computer running?
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

Miriam2 - The longer you need to keep your computer on when the power goes out, the more you need to spend on the equipment. That's about it. I priced my UPS for a short time because it's cheaper.

As for leaving the house for an hour or 2, you should always save what you're working on before you leave. If the power goes out on a home computer, it's really not a big deal - as long as you saved your stuff (it's important enough to repeat). Close out Quicken, close out Word, Excel, or whatever you're using.

If the power drops, the computer will manage things when it reboots and you won't lose anything. That's the theory...

A UPS is used for unplanned power outages. I didn't have time to save my stuff, which causes me a lot of grief.

Business users (and website servers) can't tolerate a single (cycle) drop in power. They're on a UPS - and some have backup UPS for redundancy.
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Re: A primer on backup battery systems for power outages

Post by hudson »

Miriam2,

You leave your house with your computer on. It is hooked up to the UPS. The one that you specified is fine.
When the power goes off, your UPS will hold up your computer for a while, then it will cut off...so will your computer.
The UPS should still protect against surges. Your computer should stay off. I would say that you are OK with that UPS; no more effort is needed. Note: unsaved files will not be saved.

Many UPS's have shut down software. I don't use that software except in rare conditions...business uses....not home use. The shut down software that I've used is for advanced users.

My computer is beside of my modem, a switch, and my google router; I plug them all into a 1000VA UPS. I would say that that holds everything up about 30 minutes. By default when the power goes out, it beeps once then is quiet. https://www.amazon.com/gp/product/B000B ... UTF8&psc=1

For the family computer, I use a 600VA UPS. I like a little overkill on UPSs. https://www.amazon.com/gp/product/B0010 ... UTF8&psc=1

I think that Tripp-Lite UPSs are a notch better than APC UPSs....purely a non-scientific opinion.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

whomever wrote: Wed Aug 19, 2020 6:03 pm "It seems like the Li-Ion battery packs like the ones linked earlier (jackery, etc) are the equivalent of mainstream e-bikes. They just work. You don't need to know all the ins and outs, just plug it in to use it, keep an eye on the gauge, use a generator (or solar panels) to recharge it as necessary. Ideal to pair with a generator. "

One caveat about 'pair with a generator'. Ideally, I would think you would want the generator to be able to charge at high rates (so the generator doesn't have to run a long time). Some of the 'solar generators' don't allow high charge rates. For example, my Jackery 240 uses a common input jack for charging via solar panels or 12V (from a car or generator). It does that, I think, because if it tried to draw too much current from a car cigarette lighter port it could blow the car's fuse. The upshot is that is takes several hours to charge no matter how many panels or what kind of generator you connect it to.

There are others that have higher limits (by having separate input jacks for car charging and solar panels or other 12V source). In any event, this is something you want to check.

Another point on cost: AFAIK, the batteries in the Jackery et al aren't intended to be replaceable, so when the batteries reach end of life you get to throw away the inverter and so on as well. With a DIY with discrete parts, you just buy a new battery. The jackery, IMHO, is great for a portable, but I think I would lean towards building one for a stationary application.
And, of course, the big drawback with something like a Jackery 240 is that it only has 240 watts hours of battery power. That's fine if you're just charging phones, tablets, other USB devices, and charging up AA and AAA batteries, but it's not enough for much else. My small laptop alone would drain it in under five hours.

Something else that's a problem with these battery packs is that they have several single points of failure, something to be avoided in critical systems of any kind. If there's a problem with the charger, the battery, or the inverter, the whole thing becomes unusable. With a DIY system, you can replace problematic components. For that reason, I have multiple chargers and multiple inverters.
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Re: A primer on backup battery systems for power outages

Post by iamlucky13 »

smitcat wrote: Wed Aug 19, 2020 10:45 am Agreed - while you can get much better details on this at boating and RV sites this article has a summary that may be useful:

https://homeguides.sfgate.com/run-refri ... 49672.html

"Lead-acid rechargeable batteries are rated in ampere-hours. A typical battery rated at 105 ampere hours can deliver 105 DC amps for one hour before it runs out of power. In general, you risk damage if a rechargeable lead-acid battery is drained below 50 percent of capacity, so you safely can draw 105 amps for only 30 minutes. A fridge drawing only 55 DC amps can be run for about 60 minutes of continuous duty off a 105 ampere-hour battery.
Part of this is not really accurate. Deep discharges increase aging, but don't acutely damage the battery, and there's nothing significant about 50%. Lead-acid batteries experience gradual increases in cycle aging the deeper you cycle.

Deep cycle battery lives are typically based on 80% depth of discharge - well beyond 50% - and good ones should last several hundred cycles. Commercial grade lead acid battery datasheets will even specify curves for how many cycles you should expect based on depth of discharge.

Because the effect is non-linear, it is more cost effective to do shallow discharges if practical, but when we're talking about batteries used for backup power that are only cycled a couple times a year, you're better off using that deep cycle capability than over-sizing your battery bank.
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Re: A primer on backup battery systems for power outages

Post by smitcat »

iamlucky13 wrote: Thu Aug 20, 2020 2:04 am
smitcat wrote: Wed Aug 19, 2020 10:45 am Agreed - while you can get much better details on this at boating and RV sites this article has a summary that may be useful:

https://homeguides.sfgate.com/run-refri ... 49672.html

"Lead-acid rechargeable batteries are rated in ampere-hours. A typical battery rated at 105 ampere hours can deliver 105 DC amps for one hour before it runs out of power. In general, you risk damage if a rechargeable lead-acid battery is drained below 50 percent of capacity, so you safely can draw 105 amps for only 30 minutes. A fridge drawing only 55 DC amps can be run for about 60 minutes of continuous duty off a 105 ampere-hour battery.
Part of this is not really accurate. Deep discharges increase aging, but don't acutely damage the battery, and there's nothing significant about 50%. Lead-acid batteries experience gradual increases in cycle aging the deeper you cycle.

Deep cycle battery lives are typically based on 80% depth of discharge - well beyond 50% - and good ones should last several hundred cycles. Commercial grade lead acid battery datasheets will even specify curves for how many cycles you should expect based on depth of discharge.

Because the effect is non-linear, it is more cost effective to do shallow discharges if practical, but when we're talking about batteries used for backup power that are only cycled a couple times a year, you're better off using that deep cycle capability than over-sizing your battery bank.
Yes - true deep cycle batteries are capable of a larger discharge than 50%. For a typical battery size that was being discussed here the difference in time to run that full sized refrigerator will not really help. Additionally that would depend on the actual state of the battery upon use, the ability to have good battery storage, monitoring and a reasonably decent inverter.
The question becomes - in the end does it really make sence to have something like 6 large deep cycle 6 volt cells and all the associated support hardware to run a refrigerator for 3 days?
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Re: A primer on backup battery systems for power outages

Post by linuxizer »

Not much of the discussion is focused yet on batteries as a complement to a generator. To me, having bought a small gen, that's the best use case:
- Batteries get you lights and wifi and phone charging for brief outages without even pulling out the gen
- They also let you run the generator discontinuously. A UPS on the wifi that lasts 10 hours and charges in 2 means you can run generator 2-3 times per day for 2-3 hours and still do work, etc.
- battery bank for fridge let's you do the same. Fridge won't need it to stay cold for a few hours if you don't open it, but if you want to cook with gen off....
- house leds would be fine with battery bank plus an inverter, but you'd want the panel powered, so need a much more complicated setup. Having a hard time envisioning a safe and code compliant double transfer switch (gen and batteries) that also lets the gen charge the batteries when it's being run. Seems not worth it unless there's electrical hardware designed specifically for this use case.

EDIT: Nevermind, it does exist , more here. At first glance, this looks amazing.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

linuxizer wrote: Thu Aug 20, 2020 6:21 am Not much of the discussion is focused yet on batteries as a complement to a generator. To me, having bought a small gen, that's the best use case:
- Batteries get you lights and wifi and phone charging for brief outages without even pulling out the gen
- They also let you run the generator discontinuously. A UPS on the wifi that lasts 10 hours and charges in 2 means you can run generator 2-3 times per day for 2-3 hours and still do work, etc.
- battery bank for fridge let's you do the same. Fridge won't need it to stay cold for a few hours if you don't open it, but if you want to cook with gen off....
- house leds would be fine with battery bank plus an inverter, but you'd want the panel powered, so need a much more complicated setup. Having a hard time envisioning a safe and code compliant double transfer switch (gen and batteries) that also lets the gen charge the batteries when it's being run. Seems not worth it unless there's electrical hardware designed specifically for this use case.

EDIT: Nevermind, it does exist , more here. At first glance, this looks amazing.
I've heard one person liken the generator and battery combination to that of a diesel submarines, which use the same approach. It's also the same concept as that used by hybrid vehicles, and, just like hybrid vehicles, it's a far more efficient use of a limited supply of fuel. Plus, it enables you to have some power without running a generator, which can be a beacon for those without wholesome intentions during a power outage.
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Re: A primer on backup battery systems for power outages

Post by mervinj7 »

willthrill81 wrote: Tue Aug 18, 2020 2:01 pm
mervinj7 wrote: Tue Aug 18, 2020 1:52 pm hey Will,
What's your opinion on the newish portable Lithium Ion "solar power station"? Some of my neighbors have been using it for their medical fridges. In our PG&E territory in CA, there is a high chance of a rolling blackout. They are typically 1-2 hours but some outages have been as long as 10 hours. Some of the larger ones include:

https://ecoflow.com/products/ecoflow-de ... 81k4_hoa45
https://www.jackery.com/products/explor ... er-station
https://www.indiegogo.com/projects/blue ... er-station
The EcoFlow only has 1,260 watt hours of capacity. You could buy a lead acid battery of that size, a 15 amp charger, and a 1,000 watt pure sine wave inverter for around $400 rather than $1,400. True, the EcoFlow will recharge faster and is lighter and more portable, so it's a question as to whether those benefits are worth an additional $1,000. This is also true of the Jackery, though it's only $1,000. The Indiegogo seems ridiculously expensive.
I see what you mean. It's quite a premium for convenience. That said, I can see why it's recommended for folks with small medical fridges and CPAP machines that need to be running during blackouts. I certainly wouldn't recommend a DIY solution for them unless they were really comfortable with electronics, loose wiring, and multimeters.

For myself, I just ordered a 1000W pure sine wave inverter to attach to my Nissan Leaf as suggested by fellow boglehead RustyShackleford. Might as well take advantage of the giant 40kWh "portable" battery just sitting in my driveway. Should run a regular sized fridge for days before it needs a quick charge.
viewtopic.php?p=4825288#p4825288

Recently, they released a retail solution for true vehicle to home but it's $4K just for the box, not including installation.

https://insideevs.com/news/406994/wallb ... ing-to-us/
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

That brings up another aspect - sine wave vs. square wave inverters.

I understand the differences and how they work. The choice depends on the application.

I don't have any real-world experience for the applications in this thread, so I won't provide an opinion. Googling "compare pure sine wave square wave inverter" is helpful.
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Re: A primer on backup battery systems for power outages

Post by linuxizer »

willthrill81 wrote: Thu Aug 20, 2020 10:45 amI've heard one person liken the generator and battery combination to that of a diesel submarines, which use the same approach. It's also the same concept as that used by hybrid vehicles, and, just like hybrid vehicles, it's a far more efficient use of a limited supply of fuel. Plus, it enables you to have some power without running a generator, which can be a beacon for those without wholesome intentions during a power outage.
Exactly! That APC automatic transfer switch only has 10 circuit capability, which is a shame because it's real value is in lighting up the whole house. Some generators have wireless remotes; there are WiFi->RF bridges that could let you start the generator from a computer. Then a UPS Linux driver could sense when the battery is getting low. HomeAssistant to tie it together. You'd have the generator automatically start up when the UPS battery got low, the panel to do auto load shedding and transfer between the generator and the UPS, and a computer to allow more sophisticated things to avoid the generator cycling on and off constantly (e.g. keep gen on if load is too high and the battery will deplete rapidly). Just a pipe dream; someone should make a commercial product.
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Re: A primer on backup battery systems for power outages

Post by iamlucky13 »

linuxizer wrote: Thu Aug 20, 2020 6:21 am Not much of the discussion is focused yet on batteries as a complement to a generator. To me, having bought a small gen, that's the best use case:
- Batteries get you lights and wifi and phone charging for brief outages without even pulling out the gen
- They also let you run the generator discontinuously. A UPS on the wifi that lasts 10 hours and charges in 2 means you can run generator 2-3 times per day for 2-3 hours and still do work, etc.
- battery bank for fridge let's you do the same. Fridge won't need it to stay cold for a few hours if you don't open it, but if you want to cook with gen off....
- house leds would be fine with battery bank plus an inverter, but you'd want the panel powered, so need a much more complicated setup. Having a hard time envisioning a safe and code compliant double transfer switch (gen and batteries) that also lets the gen charge the batteries when it's being run. Seems not worth it unless there's electrical hardware designed specifically for this use case.

EDIT: Nevermind, it does exist , more here. At first glance, this looks amazing.
That's a fairly common setup for people who are off-grid. They'll rely on solar power as much as possible, but keep the batteries topped off with a small generator during high demand or low production periods. The Honda inverter generators are really popular for this because they're quiet, efficient, and reliable.

As a method for backup power, the cost of this kind of setup can balloon very fast compared to just keeping extra gas on hand for the generator.

Overall, I view batteries as fitting in two places for backup applications, with a gap in between that's more cost effectively filled by a generator alone.

1) Minimal demand backup like keeping a minimal number of devices running (medical equipment, mobile devices, a light or two, perhaps a modem, and maybe as much as a fridge if you're careful) for a limited amount of time.
2) Moderate demand backup for people who already have solar panels, keeping most daily conveniences available, running air handlers for gas heating systems, and potentially even running a heat pump or air conditioner. Even in this case, a generator can be more cost effective for a given amount of energy availability, but the low noise and low maintenance of batteries can have a high appeal, and you don't have to worry about running out of fuel if an unusually long outage occurs.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

LadyGeek wrote: Thu Aug 20, 2020 11:51 am That brings up another aspect - sine wave vs. square wave inverters.

I understand the differences and how they work. The choice depends on the application.

I don't have any real-world experience for the applications in this thread, so I won't provide an opinion. Googling "compare pure sine wave square wave inverter" is helpful.
I own and have used both. You're right that Google is helpful for understanding the difference. The short answer is that pure sine wave inverters are designed to much more closely replicate the type of AC power that you get from the grid than are modified sine wave inverters.

In my experience, anything that uses an AC to DC converter (i.e. it either has a blocky plug in to the AC outlet or has a little box connected to the power plug which then goes to the device), including laptops and USB powered devices, runs fine from a modified sine wave inverter. This is because the converter is taking the AC power and converting it to DC for the device to consume. Small motors like those used in table fans and such work fine from modified sine wave power also. However, the compressors in modern refrigerators and freezers I've tried simply will not run at all on modified sine wave power but run without any issue on pure sine wave power, as long as the inverter can supply adequate power; I've tried four such refrigerator and/or freezers, and all of them did this.

Modified sine wave inverters are less expensive, but the price premium for pure sine wave inverters has dropped dramatically over the last decade. I just got a 1,000 watt Bestek pure sine wave inverter for $159 on Amazon, and in my tests so far, it's worked perfectly.

As such, I think that it's a good idea to have at least one ~150 watt modified sine wave inverter that can plug into a 12 volt outlet. These are only about $20, and they're useful for powering those non-compressor small loads. They're convenient as well on road trips if you want to power something like a laptop for a passenger or similar devices. However, for a home battery system, I would recommend having at least one pure sine wave inverter with at least 500 watts of capacity. Even though it's not a good idea to run a refrigerator or freezer from a small backup battery system, you can connect the inverter to your vehicle's battery, idle the vehicle, and then run the refrigerator or freezer.
Last edited by willthrill81 on Thu Aug 20, 2020 4:16 pm, edited 1 time in total.
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

^^^ Good info, thanks. My experience with power supplies is in high-end audiophile equipment (as a hobby). Anything which deviates from a pure sine wave creates harmonics. The DC supply then becomes a (DC + AC high frequency distortion) supply and mixes with the transistors in the power amplifier section - where you have high current draw. It's noticeable.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

LadyGeek wrote: Thu Aug 20, 2020 2:41 pm ^^^ Good info, thanks. My experience with power supplies is in high-end audiophile equipment (as a hobby). Anything which deviates from a pure sine wave creates harmonics. The DC supply then becomes a (DC + AC high frequency distortion) supply and mixes with the transistors in the power amplifier section - where you have high current draw. It's noticeable.
Yes, you can definitely notice such seemingly subtle power differences in very sensitive equipment like that. The same is true of ham radio equipment.

I did once notice the sound on a laptop computer having a faint buzzing when I powered it from a modified sine wave inverter, so I definitely know what you're talking about.

Of course, audiophiles and ham radio operators who want to operate their equipment on a battery backup probably don't mind paying extra for pure sine wave inverters.
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Re: A primer on backup battery systems for power outages

Post by inbox788 »

telemark wrote: Wed Aug 19, 2020 3:35 amThe model in question has a very common and easily replaceable battery.
I didn't notice the specific model. I have a similar one, but older and the plugs are rotated 90 degrees, so mine has higher chance of obstructed outlets. I don't know if mine is hot swappable, but the "network" ones is designed to have the battery changed without unplugging or stopping anything. I don't think you even need a screwdriver. And the connectors are different sizes, so you can't plug it in reverse. Nearly dummy proof.
hudson wrote: Wed Aug 19, 2020 4:42 amYears ago, where I worked, there was a demand for a mobile computer cart. I asked an electrical engineer/computer specialist over the phone how to do that. He immediately said, "deep cycle marine battery."
I'd be concerned about venting requirements for indoor use. Proceed with caution.
go_mets wrote: Wed Aug 19, 2020 9:34 amI haven't bought a Kill-a-watt yet.
I fried my Kill-a-watt. Apparently it's easy to do, so be careful not to overload it or learn to fix it. I went looking for a better device, but didn't find one; one that is cost effective and isn't too fragile. I threw it away, but maybe I should have kept it and fixed it. Some people disable the safety thermal fuse to prevent the problem, but I wouldn't or couldn't do that.
smitcat wrote: Wed Aug 19, 2020 9:57 amWe know this from our refrigerators at work which have thermometers on the outside reading inside.
I have an indoor/outdoor thermometer with wireless outdoor sensor. I have used these to check the refrigerator and/or freezer temperature at times.
tyrion wrote: Wed Aug 19, 2020 11:39 amPersonally, I am getting Tesla PowerWalls installed in a few months. Combined with solar and in a very sunny location it should keep us running in almost all scenarios. The 2 batteries will hold almost a days worth of standard energy for us (assuming limited AC). If we strip away the stuff we would turn off in a grid outage (pool pump, hot tub, oven, etc) it would be closer to 2-3 days.
As the costs of solar panels and batteries comes down, being off the grid or getting off the grid will get very interesting. Home phones are disappearing, first POTS and now VOIP. Folks are cutting the cable. Ethernet wiring in the home is no longer needed. Energy independence is taking on a new meaning, and what we're looking as backup power to the grid is slowly becoming the primary power for basic needs. I don't like having all these battery devices, but with solar outdoor LED lighting, they're so easy that I'm putting the all over the outside fence and yard. The ones in the past would die in less than a year, but the current ones might last a few years, and when it's time to change the battery, it might be simpler or cheaper to replace the whole thing. Indoors, critical lighting needs use very little power and having prioritized circuits for refrigerator and other critical appliances could conceivably last a long time. You wouldn't be swimming or doing laundry if power was limited. Eating and internet are probably top priorities, and they don't have to use a lot of electricity. AC and heating might be the big power hogs, depending on the weather and you may have other heating alternatives.
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Re: A primer on backup battery systems for power outages

Post by hudson »

inbox788 wrote: Thu Aug 20, 2020 5:47 pm
hudson wrote: Wed Aug 19, 2020 4:42 amYears ago, where I worked, there was a demand for a mobile computer cart. I asked an electrical engineer/computer specialist over the phone how to do that. He immediately said, "deep cycle marine battery."
I'd be concerned about venting requirements for indoor use. Proceed with caution.
My thinking exactly; I didn't think about the venting requirements. There was no way I was going to cobble together something with open battery terminals on a rolling cart. I ordered a commercial version something like you see in hospitals. I was not an engineer....out of my field. I had no problem adding an industrial computer with wifi and a monitor...that was my field.
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Re: A primer on backup battery systems for power outages

Post by willthrill81 »

hudson wrote: Thu Aug 20, 2020 7:31 pm
inbox788 wrote: Thu Aug 20, 2020 5:47 pm
hudson wrote: Wed Aug 19, 2020 4:42 amYears ago, where I worked, there was a demand for a mobile computer cart. I asked an electrical engineer/computer specialist over the phone how to do that. He immediately said, "deep cycle marine battery."
I'd be concerned about venting requirements for indoor use. Proceed with caution.
My thinking exactly; I didn't think about the venting requirements. There was no way I was going to cobble together something with open battery terminals on a rolling cart. I ordered a commercial version something like you see in hospitals. I was not an engineer....out of my field. I had no problem adding an industrial computer with wifi and a monitor...that was my field.
The need for venting lead acid batteries is very overrated. As I noted in the OP, hydrogen is the lightest element in the universe and races straight upward at 45 miles per hour once it's freed from its oxygen companion in water. Unless you have the batteries stored in an airtight space, the hydrogen will easily escape. I've never once heard even a rumor of anyone with a home battery system having an issue.

Think about this. There are tens of millions of vehicles on the road in the U.S. alone, virtually all of which have lead acid batteries stored right next to large internal combustion engines that get quite hot, and yet battery accidents in even this situation of any kind are extraordinarily rare. Even when accidents do occur, about the worst thing that happens is some battery acid splashes on to someone. For that reason, you should wear eye protection and gloves when working with lead acid batteries.

You're taking on FAR greater risk every time you set foot in a vehicle that you will ever experience from a home backup battery system.
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Re: A primer on backup battery systems for power outages

Post by ballons »

LadyGeek wrote: Wed Aug 19, 2020 10:20 am I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
Something is wrong with that fridge or the seals are bad. You should be able to make it at least 24 hours. Your food will be icy and freezer burnt.

Buy a chest freezer and you can go 48 hours or longer. I've seen upright freezers marketed as 48 hours as well.
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Re: A primer on backup battery systems for power outages

Post by smitcat »

ballons wrote: Fri Aug 21, 2020 12:32 am
LadyGeek wrote: Wed Aug 19, 2020 10:20 am I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
Something is wrong with that fridge or the seals are bad. You should be able to make it at least 24 hours. Your food will be icy and freezer burnt.

Buy a chest freezer and you can go 48 hours or longer. I've seen upright freezers marketed as 48 hours as well.
In the case of power outage it does make a larger difference where these people might be - in some cases with the power out the temps outside the freezer might be 50 degrees where in other places the temps might be 90 degrees.
You can put a couple of ice cubes in a zip lock bag and leave it in the front of your freezer - it will tell you if the temps have moved above freezing while you were not aware.
Some will be very surprised at how long they last or do not last.
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Re: A primer on backup battery systems for power outages

Post by smitcat »

Most common data from online sources....

"Without power, a refrigerator will likely remain at a safe temperature for up to four hours if the door is kept closed, Tamika Sims, PhD, director of food technology communications at the International Food Information Council, tells Health. Food in your freezer stays cold for even longer—about a day if the freezer is half full, and about 48 hours if it’s full (the more food there is inside, the more cold is retained). "
Link - https://www.health.com/food/how-long-fo ... e-no-power
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Re: A primer on backup battery systems for power outages

Post by LadyGeek »

smitcat wrote: Fri Aug 21, 2020 7:52 am
ballons wrote: Fri Aug 21, 2020 12:32 am
LadyGeek wrote: Wed Aug 19, 2020 10:20 am I don't see any mention about a freezer. Refrigerators also have freezer sections.

I general rule of thumb is that a freezer should go no longer than 12 hours without power. Once the food is thawed, it needs to be cooked soon (put it in the fridge) or discarded.

When I'm on a generator, I always have it turned on for a few hours in the morning, mid-day, and evening.
Something is wrong with that fridge or the seals are bad. You should be able to make it at least 24 hours. Your food will be icy and freezer burnt.

Buy a chest freezer and you can go 48 hours or longer. I've seen upright freezers marketed as 48 hours as well.
In the case of power outage it does make a larger difference where these people might be - in some cases with the power out the temps outside the freezer might be 50 degrees where in other places the temps might be 90 degrees.
You can put a couple of ice cubes in a zip lock bag and leave it in the front of your freezer - it will tell you if the temps have moved above freezing while you were not aware.
Some will be very surprised at how long they last or do not last.
In a follow-up post, I explained where the 12 hours came from (keeping fish in a cooler packed with ice). willthrill81 promptly corrected me about freezer temperatures - it's much colder than an ice-packed cooler.

This is an upright freezer I have in my basement. It's separate from my kitchen refrigerator / freezer.

I agree that the ambient temperature has much to do with how long your food will last. The higher the ambient temperature, the harder your freezer needs to work to maintain temperature.

A chest freezer is a good suggestion if anything happens to the one I'm using now.
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Re: A primer on backup battery systems for power outages

Post by glock19 »

I have a questions about UPS's. When commercial power is available, is the connected device powered from the UPS's battery (which is being constantly charged), or is the AC just passing through the UPS and powering the device?

There is another current thread debating the benefits of whole house generators. I use a combination of APC and CyberPower UPS along with a Generac 22KW standby generator. When I loose commercial power there is a 15 sec delay before my generator powers up. The UPS's keep computers, modem, router, switches, and TV equipment powered until generator power takes over. Maybe a little more cost than some want to invest, but it's nice to know that when I'm away from home life will go on uninterrupted.
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Re: A primer on backup battery systems for power outages

Post by linuxizer »

glock19 wrote: Fri Aug 21, 2020 9:01 am I have a questions about UPS's. When commercial power is available, is the connected device powered from the UPS's battery (which is being constantly charged), or is the AC just passing through the UPS and powering the device
Consumer UPSs do the latter. Some enterprise UPSs are double conversion which means you're always running off the battery. If you have an inverter gen, I suspect you'll be OK with single conversation.
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Re: A primer on backup battery systems for power outages

Post by hudson »

glock19 wrote: Fri Aug 21, 2020 9:01 am I have a questions about UPS's. When commercial power is available, is the connected device powered from the UPS's battery (which is being constantly charged), or is the AC just passing through the UPS and powering the device?

There is another current thread debating the benefits of whole house generators. I use a combination of APC and CyberPower UPS along with a Generac 22KW standby generator. When I loose commercial power there is a 15 sec delay before my generator powers up. The UPS's keep computers, modem, router, switches, and TV equipment powered until generator power takes over. Maybe a little more cost than some want to invest, but it's nice to know that when I'm away from home life will go on uninterrupted.
Somebody correct me if I'm wrong, but I think the home UPSs deliver steady and clean power to plugged in devices. The plugged in devices are spared from drops in power, spikes, and surges. The UPS delivers the good stuff. You can read the details for a UPS that I use: https://www.amazon.com/gp/product/B000B ... UTF8&psc=1
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Re: A primer on backup battery systems for power outages

Post by linuxizer »

hudson wrote: Fri Aug 21, 2020 9:35 amSomebody correct me if I'm wrong, but I think the home UPSs deliver steady and clean power to plugged in devices. The plugged in devices are spared from drops in power, spikes, and surges. The UPS delivers the good stuff. You can read the details for a UPS that I use: https://www.amazon.com/gp/product/B000B ... UTF8&psc=1
Unless you're paying a lot more for "double conversion," your unit passes through the utility power and switched to the battery the instant it detects a power loss. Should be fine unless your generator produces such noisy power that the UPS detects it as a power loss and constantly switches back on and off as the power fluctuates.
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Re: A primer on backup battery systems for power outages

Post by hudson »

linuxizer wrote: Fri Aug 21, 2020 10:17 am
hudson wrote: Fri Aug 21, 2020 9:35 amSomebody correct me if I'm wrong, but I think the home UPSs deliver steady and clean power to plugged in devices. The plugged in devices are spared from drops in power, spikes, and surges. The UPS delivers the good stuff. You can read the details for a UPS that I use: https://www.amazon.com/gp/product/B000B ... UTF8&psc=1
Unless you're paying a lot more for "double conversion," your unit passes through the utility power and switched to the battery the instant it detects a power loss. Should be fine unless your generator produces such noisy power that the UPS detects it as a power loss and constantly switches back on and off as the power fluctuates.
Thanks linuxizer! I had to look it up. This article has a nice table comparing standard UPSs with double conversion UPSs.
https://www.qpsolutions.net/2019/11/lin ... ones-best/

I remember reading about double conversion when buying a washing machine sized UPS....long ago. The double conversion system works by converting power from AC to DC and then back to AC.

Bottom Line: Standard UPSs are probably fine for home use.

If you're doing a server room where your trying to achieve 100% up time, go for a double conversion UPS among other things.
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Re: A primer on backup battery systems for power outages

Post by mrc »

I owned a ~3500w inverter generator that wasn't large enough to run essentials during prolonged power outages. I replaced it with an 8000w Genrac and found out after the fact that my APC UPS won't run on the Genrac power. Something I wish I had considered before the switch.
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Re: A primer on backup battery systems for power outages

Post by sport »

willthrill81 wrote: Thu Aug 20, 2020 11:15 pm
Think about this. There are tens of millions of vehicles on the road in the U.S. alone, virtually all of which have lead acid batteries stored right next to large internal combustion engines that get quite hot, and yet battery accidents in even this situation of any kind are extraordinarily rare. Even when accidents do occur, about the worst thing that happens is some battery acid splashes on to someone. For that reason, you should wear eye protection and gloves when working with lead acid batteries.
When the hydrogen in a car battery is ignited, splashing battery acid, while hazardous, is not the "worst thing that can happen". When a battery explodes, jagged pieces of the battery cover become projectiles. This can put out an eye. Battery acid in the eyes is bad, but survivable. Battery acid will not cause meaningful damage to your hands, so gloves are not necessary. However, as you say, eye protection is a must. My knowledge of this comes from years of working in a battery test lab, and developing devices to minimize the chance of battery explosions.
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