What's wrong with my Roomba battery?

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knightrider
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What's wrong with my Roomba battery?

Post by knightrider »

Bought a non-OEM one and after five months of use I get "charging errors". Using my voltmeter I only measure 3.2 volts when I believe I am supposed to get 14.4 . 3.2 volts implies many of the cells are just dead. How is that possible? I probably only used it a dozen times and each time it lasted for a full 1-2 hours.

How come something work perfectly then all of a sudden die?
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anon_investor
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Re: What's wrong with my Roomba battery?

Post by anon_investor »

Maybe buy a real one next time? If non oem, quality control may be suspect.
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lthenderson
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Re: What's wrong with my Roomba battery?

Post by lthenderson »

knightrider wrote: Tue Jul 28, 2020 10:04 pm Bought a non-OEM one and after five months of use I get "charging errors". Using my voltmeter I only measure 3.2 volts when I believe I am supposed to get 14.4 . 3.2 volts implies many of the cells are just dead. How is that possible? I probably only used it a dozen times and each time it lasted for a full 1-2 hours.

How come something work perfectly then all of a sudden die?
12% of all the reviews talk about how the battery either died suddenly after a couple months or dies quickly after being charged. I've never had much luck buying non-OEM batteries when it comes to power tools or electronics.
Broken Man 1999
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Re: What's wrong with my Roomba battery?

Post by Broken Man 1999 »

Have you tried to get it replaced?

No experience with Roomba replacement batteries by Tenergy, but I have had good experiences with their rechargeable AAA, AA, 9v batteries. I bought a charger and AA and AAA rechargeable batteries in 2014 and 9v rechargeable batteries and charger in 2016, all batteries still being recharged as needed.

Broken Man 1999
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Mudpuppy
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Re: What's wrong with my Roomba battery?

Post by Mudpuppy »

The simplest explanations are either you got a random "dud" or the company has poor quality-control on their units so "duds" are more common-place. Batteries are one area where I pay for OEM parts or I go to a local battery shop that carries high-quality non-OEM brands, rather than order on Amazon.
wilked
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Re: What's wrong with my Roomba battery?

Post by wilked »

I've learned the hard way, never buy non-OEM w/ batteries. Tried it recently with 20V Dewalt and got exactly what I paid for
adamthesmythe
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Re: What's wrong with my Roomba battery?

Post by adamthesmythe »

You don't really want to know what is wrong with the battery. (To find that out...read some journals about battery reliability...take the battery to a lab and [carefully] do a postmortem...)

What you want is to express anger and frustration about having made the wrong choice of supplier.

Next time...go for OEM...or spin the roulette wheel again. Reviews might give you an idea what the house percentage is.
iamlucky13
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Re: What's wrong with my Roomba battery?

Post by iamlucky13 »

Tenergy is a brand I've seen in use before. They're a discount brand, but their reputation for making less common sizes of NiMH cells is ok, as far as I know.

However, NiMH can be sensitive to overcharging and over-discharging, and that can make certain factors which don't matter much if charged individually really critical when they are charged in multi-cell packs like this.

If they are used to the limit of their capacity, then differences in individual cell capacity means some will be more discharged than others. These then have faster loss of capacity, and the effect accelerates. If they get low enough, then the batteries in better condition that they are in series with can cause an effect called voltage reversal which can significantly accelerate their decline.

It may be that Tenergy is not able to achieve as consistent of cell performance as whoever Roomba's OE supplier is (probably FDK, formerly Sanyo, the maker of the Eneloop brand), making them more likely to experience this sort of runaway capacity loss. And as a discount brand, they probably don't do life cycle tests on their battery packs to discover issues like this.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

iamlucky13 wrote: Wed Jul 29, 2020 2:59 pm However, NiMH can be sensitive to overcharging and over-discharging, and that can make certain factors which don't matter much if charged individually really critical when they are charged in multi-cell packs like this.

Perhaps you are right. Still surprising that something so ubiquitous can be be so failure-prone. I've experienced similar failures for other non-OEM Roomba batteries but that was usually after a year, not five months. Now I am done with Roomba. Bad for the wallet and environment to keep buying these expensive batteries every year.

I wonder if Tesla electric cars have the same issue? All of a sudden they just don't charge?!
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anon_investor
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Re: What's wrong with my Roomba battery?

Post by anon_investor »

knightrider wrote: Thu Jul 30, 2020 8:22 am
iamlucky13 wrote: Wed Jul 29, 2020 2:59 pm However, NiMH can be sensitive to overcharging and over-discharging, and that can make certain factors which don't matter much if charged individually really critical when they are charged in multi-cell packs like this.

Perhaps you are right. Still surprising that something so ubiquitous can be be so failure-prone. I've experienced similar failures for other non-OEM Roomba batteries but that was usually after a year, not five months. Now I am done with Roomba. Bad for the wallet and environment to keep buying these expensive batteries every year.

I wonder if Tesla electric cars have the same issue? All of a sudden they just don't charge?!
How long have you had your Roomba for? Do you use it daily? I have had mine for several years and I am still using the original battery.
onourway
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Re: What's wrong with my Roomba battery?

Post by onourway »

knightrider wrote: Thu Jul 30, 2020 8:22 am
iamlucky13 wrote: Wed Jul 29, 2020 2:59 pm However, NiMH can be sensitive to overcharging and over-discharging, and that can make certain factors which don't matter much if charged individually really critical when they are charged in multi-cell packs like this.

Perhaps you are right. Still surprising that something so ubiquitous can be be so failure-prone. I've experienced similar failures for other non-OEM Roomba batteries but that was usually after a year, not five months. Now I am done with Roomba. Bad for the wallet and environment to keep buying these expensive batteries every year.

I wonder if Tesla electric cars have the same issue? All of a sudden they just don't charge?!
Tesla has insane QC and software control over their batteries, so they don't have this problem, generally.

Usually OEM batteries are at least decent on this for any name-brand product because it directly affects whether people will continue to buy their products - just as you feel now. Did you contact Roomba if your original battery if it failed after ~1 year? I would be surprised if they would not have replaced them.

Tenergy is generally a decent name brand - however with Amazon you never really know what you are getting. It could very well be something really cheap with a Tenergy sticker. I would not pin this one on Roomba.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

anon_investor wrote: Thu Jul 30, 2020 8:26 am How long have you had your Roomba for? Do you use it daily? I have had mine for several years and I am still using the original battery.
Had it for eight years. But I don't use it daily. More like once every 2-3 weeks..
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anon_investor
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Re: What's wrong with my Roomba battery?

Post by anon_investor »

knightrider wrote: Thu Jul 30, 2020 8:58 am
anon_investor wrote: Thu Jul 30, 2020 8:26 am How long have you had your Roomba for? Do you use it daily? I have had mine for several years and I am still using the original battery.
Had it for eight years. But I don't use it daily. More like once every 2-3 weeks..
Ah, 8 years, that makes sense then, most batteries rarely last that long.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

anon_investor wrote: Thu Jul 30, 2020 9:15 am Ah, 8 years, that makes sense then, most batteries rarely last that long.
I've gone through several batteries in the 8 years. I think all were non OEM and none lasted more than 1-2 years. The most recent one lasted just five months.. Hence my frustration with this technology..
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anon_investor
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Re: What's wrong with my Roomba battery?

Post by anon_investor »

knightrider wrote: Thu Jul 30, 2020 9:17 am
anon_investor wrote: Thu Jul 30, 2020 9:15 am Ah, 8 years, that makes sense then, most batteries rarely last that long.
I've gone through several batteries in the 8 years. I think all were non OEM and none lasted more than 1-2 years. The most recent one lasted just five months.. Hence my frustration with this technology..
How long did the original OEM one last? It might be the case where a single more expensive OEM one would have lasted longer and saved you money in the long run.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

anon_investor wrote: Thu Jul 30, 2020 9:22 am How long did the original OEM one last? It might be the case where a single more expensive OEM one would have lasted longer and saved you money in the long run.
Unfortunately I don't know as I bought it used :-)
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beernutz
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Re: What's wrong with my Roomba battery?

Post by beernutz »

We took our OEM Roomba 985 back to Costco for a return after 7 months. When it worked it was great but ours would get stuck many places. I bought 2 more invisible walls giving us a total of 3 to block off the worst sticking points but it would still find new ones.

Then it developed the circle of death (google it) where it would leave the charging station but only be able to turn in one direction for a few seconds and then error out. No amount of cleaning would revive it so back to Costco it went and Costco god bless them didn't blink. I'm still out the $50+ for the 2 extra invisible walls which were bought on Amazon and were out of the return window.
Don't gamble; take all your savings and buy some good stock and hold it till it goes up, then sell it. If it don't go up, don't buy it. --Will Rogers
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anon_investor
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Re: What's wrong with my Roomba battery?

Post by anon_investor »

knightrider wrote: Thu Jul 30, 2020 9:26 am
anon_investor wrote: Thu Jul 30, 2020 9:22 am How long did the original OEM one last? It might be the case where a single more expensive OEM one would have lasted longer and saved you money in the long run.
Unfortunately I don't know as I bought it used :-)
:shock: . That might explain it...
wilked
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Re: What's wrong with my Roomba battery?

Post by wilked »

Used my Roomba for years, it cleans daily, battery runs plenty strong, never replaced. I would not be surprised with a battery replacement needed every 5-8 years, similar I would expect to my iPhone which is charged daily and does need a battery replaced on some periodic basis (numbering years)
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

iamlucky13 wrote: Wed Jul 29, 2020 2:59 pm However, NiMH can be sensitive to overcharging and over-discharging, and that can make certain factors which don't matter much if charged individually really critical when they are charged in multi-cell packs like this.
I wonder why these NiMH cells don't have some kind of microchip to "remember" their charging history? These things aren't cheap, ~$25+. Even a few dollar kids toy will have chips inside it I think?
jharkin
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Re: What's wrong with my Roomba battery?

Post by jharkin »

Probably a bad pack.

Since that's a NiMH, either stick to OEM, or if you go aftermarket look for a vendor that guarantees they use genuine factory fresh Sanyo or Panasonic cells (those are the gold standard for NiMH and NiCD)
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Re: What's wrong with my Roomba battery?

Post by Mudpuppy »

knightrider wrote: Thu Jul 30, 2020 8:58 am
anon_investor wrote: Thu Jul 30, 2020 8:26 am How long have you had your Roomba for? Do you use it daily? I have had mine for several years and I am still using the original battery.
Had it for eight years. But I don't use it daily. More like once every 2-3 weeks..
If you're using it that infrequently, the recommendation for NiMH Roombas is to take the battery pack out between uses to preserve battery life. NiMH does not do well when sitting on a charger for a long period of time. It goes through too many short discharge / recharge cycles, which it does not respond well to. NiMH does best when it has a long discharge followed by a long charge.

So you might to switch to recharging it after a cleaning cycle, removing the battery, then putting it back in when you're ready for the next cleaning cycle. Or start using the Roomba more frequently so it gets a more regular duty cycle of long discharge followed by long charge.

Also, I really suspect you got a fake battery pack that is more susceptible to damage from these short cycles. Your complaint should be more with Amazon and this listing than it is with Roomba or Tenergy. Due to Amazon's co-mingling of inventory from different vendors, all it takes is one vendor with knock-off batteries that they tell Amazon are Tenergy (or Roomba or any other brand) and Amazon says "OK!" and plops all that fake inventory in the same warehouse bin as the legitimate inventory. You then play an inventory version of Russian roulette to see if you end up with the legitimate battery or the fake battery.

That's why I never buy battery packs (or SD cards or any other item where counterfeits run rampant and cause problems) from Amazon. I always buy battery packs either directly from the manufacturer or from the local battery shop.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

Mudpuppy wrote: Thu Jul 30, 2020 1:32 pm So you might to switch to recharging it after a cleaning cycle, removing the battery, then putting it back in when you're ready for the next cleaning cycle.
Not sure I follow how this will make any difference? When it in the charger it stays fully charged. Same thing if I remove it from it, no?
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Re: What's wrong with my Roomba battery?

Post by Mudpuppy »

knightrider wrote: Thu Jul 30, 2020 1:36 pm
Mudpuppy wrote: Thu Jul 30, 2020 1:32 pm So you might to switch to recharging it after a cleaning cycle, removing the battery, then putting it back in when you're ready for the next cleaning cycle.
Not sure I follow how this will make any difference? When it in the charger it stays fully charged. Same thing if I remove it from it, no?
While it is on the charger, it slowly loses charge either through natural decay or vampire power drains from the Roomba circuitry. At some point, the charger controller board on the Roomba goes "oops, getting a little low, I best top off" and it recharges the battery to 100%. But that "oops" threshold is a fairly low percentage compared to how much the battery would discharge during a cleaning cycle. So you get a whole burst of small discharges followed by small charges, and NiMH batteries do not like that.

If you take the battery out of the Roomba, you break that cycle. You'll still have a little bit of charge loss due to natural decay, but it's not much for a couple of weeks. You won't have any vampire power drains and you won't have the charger controller board constantly trying to top it off with an itty bitty charge that slowly damages the battery. Maybe it starts the next cleaning cycle at 95% power instead of 100% power, but that's not a big deal.

The battery will be much "happier" if the majority of its duty cycles are discharging from 95% power to say 25% power during a cleaning cycle, recharging to 100% power, then sitting on a shelf and having a slow decay back to 95% power before the next cleaning cycle.

Remember back in the olden days of NiMH cell phone or cordless phone batteries how they would always tell you to let the battery drain down to 30% or lower before recharging it or otherwise you might shorten its "memory" of what a full charge is? It's the same logic with the Roomba's NiMH battery. NiMH batteries do better with a large discharge followed by a large charge, rather than a bunch of tiny charge cycles.

Here's more info on NiMH batteries if you want to delve deeper: https://batteryuniversity.com/learn/art ... al_hydride
Or just scroll down to these two most relevant tips:
* Nickel-based batteries are best fast charged; a lingering slow charge causes “memory.”
* Do not leave a nickel-based battery in the charger for more than a few days. If possible, remove the packs and apply a brief charge before use.
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knightrider
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Re: What's wrong with my Roomba battery?

Post by knightrider »

Mudpuppy wrote: Thu Jul 30, 2020 1:55 pm But that "oops" threshold is a fairly low percentage compared to how much the battery would discharge during a cleaning cycle. So you get a whole burst of small discharges followed by small charges, and NiMH batteries do not like that.
Wouldn't the Roomba charging circuitry have some intelligence not to do this? If that were really the problem the solution seems quite simple.

Also instead of removing the battery isn't it easier just to unplug the charger once it's fully charged?
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Re: What's wrong with my Roomba battery?

Post by Mudpuppy »

knightrider wrote: Thu Jul 30, 2020 3:11 pm
Mudpuppy wrote: Thu Jul 30, 2020 1:55 pm But that "oops" threshold is a fairly low percentage compared to how much the battery would discharge during a cleaning cycle. So you get a whole burst of small discharges followed by small charges, and NiMH batteries do not like that.
Wouldn't the Roomba charging circuitry have some intelligence not to do this? If that were really the problem the solution seems quite simple.

Also instead of removing the battery isn't it easier just to unplug the charger once it's fully charged?
Since Roomba envisioned the primary use case is to use Roomba's several times a week with a full discharge cycle on each use, the controller board probably only has logic to enforce safety conditions in the charging cycle.This was a common approach. Back in the day when cell phones still had NiMH batteries, very few had logic to avoid too many short charging cycles, which is why the old advice was to never leave the cell phone on the charger longer than it needed to be charged. It used to be an advertising feature when the cell phone charger did have the logic to avoid short charging cycles, and there were a lot of NiMH battery-life preserving behaviors that had to be unlearned when cell phones switched to Li-Ion batteries.

You could just unplug the charger, but then the battery is still subjected to vampire drains by the Roomba circuitry. I don't have specific numbers on how extreme the vampire drain is for a Roomba, but it could be the difference between starting with say 95% charge from a battery that's been removed or starting with 85% charge for one that was left in the Roomba. The exact difference will depend on how much of a vampire drain your particular Roomba unit has.

Edit: Typo fix
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