Batteries

cj · Joined: 24 Jan 2008 Posts: 15

I've searched this site and read many messages and I'm still confused. My roomba's batteries last about 6 or 7 months then they get weak. Romba runs fine but it goes almost instantly from green to red. When the batteries are newer it would run a long time on yellow. What really ticks me off is because of this it almost never returns to his home base any more. It seems it doesn't start looking for it's base until it's in yellow and because it spends so very very little time between green and dead now it doesn't return. This is especially so when it's running on wood floor with green power then I see it hit a rug and go instantly to red and stop. It used to continue cleaning on yellow and even some red running onto and off of the carpet all the time.

So, In looking for a new battery. But first what exactly is the APS battery pack roomba came with? Is it NiCad, NiMH, other? What amp hours should I be looking for, 2400, 3300, 3800? I've seen replacement batteries listed as 3300 amp hour NiMH and they have the terminals already on them on ebay. I have already opened the pack but there is nothing written on the cells to indicate what they are either. Also keep in mind I'm using the rapid charger that came with my roomba.

I have also seen whole replacement packs but they don't list amp hours or any info and they say the color might vary which leads me to wonder if I'm getting a Roomba APC battery or the standard Roomba battery.

What should I do?

P.S. I've already played with discharging an recharging enough. I will not waste my time any more trying to recondition these batteries.

vic7767 · Joined: 14 Jan 2006 Posts: 3287 Location: Louisiana

You might want to consider changing from the stock NiMH Roomba battery cells and switch to the newer, better, last twice as long, LI-ion battery technology. They use the same case, the same home base, rapid charger, regular Roomba power supply etc. You can send a PM to me or you can send a PM to glo69 or you can vist Chris's website:

www.RoombaExchange.com

cj · Joined: 24 Jan 2008 Posts: 15

A bit to pricey for me. I'm going to try the 3.3Ah NiMH pack on ebay. I've got another dead pack here I might let Batteries Plus rebuild for me. Only thing is they don't have NiMH batteries. They want to use NiCad. I'm unsure about that.

vic7767 · Joined: 14 Jan 2006 Posts: 3287 Location: Louisiana

I don't understand too pricey..... When you consider that the LI-ion battery will last twice as long and depending on where you purchase, is not any more expensive than two of the stock Roomba NiMH batteries.

Boomerang · Joined: 15 Jun 2008 Posts: 36

cj wrote: I've searched this site and read many messages and I'm still confused. My roomba's batteries last about 6 or 7 months then they get weak.

Reading your question regarding Batteries leaves me to wonder whether you're cleaning many rooms on one charge (mission) and maybe on a daily basis too. :?

Jeff Carver · Joined: 19 Jan 2008 Posts: 113 Location: Massachusetts

New NiCad cells will give you about an hour of run time, or a little less, per charge. Don't go that route unless you routinely clean only one or two rooms a day on a charge. That said, I have a Red in my office that performs okay on cheap NiCads, but that's because it's a small space.

cj · Joined: 24 Jan 2008 Posts: 15

I turn it loose with access to the kitchen (vinyl), den (mostly low pile rug), hall (hardwood) and guest bathroom (vinyl) each morning and promptly leave for work--I hate watching it. None of my rooms are very large. When I come home I expect to find it docked and charged. I usually don't run it again till the next am. When the battery starts to go it frequently will not be docked when I get home.

I got the new pack today and got it put in the shell and installed in roomba and I think I'll let it charge for 24+ hours before using it--Maybe Wed AM. Everyone Agree?

bob_ninja · Joined: 17 Apr 2006 Posts: 174

First of all just to set your expectations you should know that NiMH batteries can last anywhere from 100 to 1000 cycles!!! The primary cause for short lifespan is hard work (such as in cleaning bots that use a lot of power) and deep discharge (going to near complete empty state).

If you get 6-7 months using it once per day, that is about 200 cycles, so clearly your batteries are stressed too much. Here are some suggestions:

- run it every other day to allow some downtime (take if off charger for 24 hours before next mission to allow to cool off)
- limit cleaning area to avoid full discharge
(limit discharge to say 40% will at least double, likely triple and quadruple batt lifespan)

So simply reduce the load. Trying a higher capacity cells might help as well. I got bigger ones (I think 3800 mAh not sure) and the pack works great so far. Note that I stop my bots when I see orange and never let them go to red if I am around)

PS: For hard working bots 200 cycles is normal. Even with best treatment you may get only 400-500 cycles.

cj · Joined: 24 Jan 2008 Posts: 15

I'm confused, the Read First FAQ topic at the top of the forum that Vic7767 pointed me to in another thread says:
Quote: "Roomba's battery can last for hundreds of charging cycles with proper care. Here are some tips to extend the life of your battery, and help keep it at the peak of performance:

Frequent use - Rechargeable nickel-based batteries do best when used frequently. The worst thing for batteries like these is infrequent light use. The Roomba was designed to be used frequently; this will keep the battery healthy.
...
Occasionally exhaust the battery - At least once every week or two, make sure to run the unit until the battery is exhausted; it will stop running and will display a red light. It is not necessary to do this every time you use it.

but I've heard others say like bob_ninja to not let it get to discharged. I usually just hit clean and I don't know how far discharged it gets before it docks.

Frankly I've heard NiCad would be better and they are what is used in my cordless drill which can see heavy but infrequent use and is holding up pretty well--about 2.5 years now. They use an inteligent rapid charger that is not supposed to overcharge. I only charge them when they seem to be slowing down.

I don't know what to think.

vic7767 · Joined: 14 Jan 2006 Posts: 3287 Location: Louisiana

LI-ion is the technology that most manufacturers are heading towards. It is the best way to go operationally, dependability, longevity, and cost are very reasonable.

The stock NiMH battery that IRobot uses will function just fine for the number of cycles specified in their statement. The frequent use reference is discussing the use of your Roomba on a daily basis. Not a deep discharge of the battery, just a cleaning cycle. The deep discharge of the NiMH battery is recommended once every 6 weeks, not every time it is used. In order to accomplish a deep discharge the Roomba should be placed in the MAX mode and allowed to run until it stops and won't begin another cleaning cycle.

cj · Joined: 24 Jan 2008 Posts: 15

according to the article you pointed me to the deep discharge should be done:
Quote: At least once every week or two
I rarely ever do a deep discharge but have tried it a few times trying to get my batteries performing better. Actually they seem to be getting worse. So, I'll see how this new pack I got on ebay performs.

vic7767 · Joined: 14 Jan 2006 Posts: 3287 Location: Louisiana

Some portions of the article may be out of date. We are all learning on a daily basis about these batteries and the latest info is not to perform a deep discharge more that once every 6 weeks. I'm sitting here with about 40 NiMH batteries and 20 LI-ion batteries for both the Roomba and Scooba. Some of the NiMH are almost 3 years old and still work. They are not used everyday, they are not deep discharged weekly but they do receive some use when removed from the shelf and installed into the Roomba crew of the week.

bob_ninja · Joined: 17 Apr 2006 Posts: 174

cj wrote: according to the article you pointed me to the deep discharge should be done:
Quote: At least once every week or two
I rarely ever do a deep discharge but have tried it a few times trying to get my batteries performing better. Actually they seem to be getting worse. So, I'll see how this new pack I got on ebay performs.

It is better to talk in terms of cycles. The so called "memory effect" was most acute in older NiCd and is far less common in modern NiMH cells. Therefore, this advice is bit old.

Using modern NiMH cells, you don't need a deep dicharge more often than 20-40 cycles. Even that may be too often. So if you use your bot once per day, then I would do deep discharge no more than once per month.

bob_ninja · Joined: 17 Apr 2006 Posts: 174

cj wrote: Quote: "Roomba's battery can last for hundreds of charging cycles with proper care. Here are some tips to extend the life of your battery, and help keep it at the peak of performance:

Frequent use - Rechargeable nickel-based batteries do best when used frequently. The worst thing for batteries like these is infrequent light use. The Roomba was designed to be used frequently; this will keep the battery healthy.
...
Occasionally exhaust the battery - At least once every week or two, make sure to run the unit until the battery is exhausted; it will stop running and will display a red light. It is not necessary to do this every time you use it.

but I've heard others say like bob_ninja to not let it get to discharged. I usually just hit clean and I don't know how far discharged it gets before it docks.

The old models used to have a "Max" button that would cause a deep discharge, drain battery to near empty. The new models don't have it, so you are correct - fro 5xx models you cannot control directly how much battery capacity is used. You can do it indirectly by limiting the area being cleaned. So if you reduce cleaning area in half then half as much power is used from a battery. Rather crude, I know. It may take some trial and error.

BTW, you'll note that the nex 5xx generation robots try to locate the base well before red status. Also Max button is removed because iRobot realized it caused too much damage and reduced battery lifespan.

cj wrote: Frankly I've heard NiCad would be better and they are what is used in my cordless drill which can see heavy but infrequent use and is holding up pretty well--about 2.5 years now. They use an inteligent rapid charger that is not supposed to overcharge. I only charge them when they seem to be slowing down.

NiCd is obsolete. Even power tools are now switching to Lithium type batteries. I now use B&D VPX and it is amazing. I still use older NiCd as well. In some cases new Lithium packs are still very expensive so NiCd is sometimes more cost effective. Considering high power requirements, robots need more than NiCd can deliver. NiCd will handle the abuse well, but their capacity is just too low. Your runtime would be reduced even more. So forget NiCd.

cj wrote: I don't know what to think.

I'll try to summirize in a simple fashion (skipping details):

- NiCd

Forget it - obsolete.

- NiMH (standard iRobot battery)

Can work for several hundred cycles, just avoid:
1) deep discharge (limit cleaning area if necessary)
2) very heavy workloads, like deep carpets and similar

- Lithium

There are actually 2 distinct generations, so:

1) Old Lithium used in laptops, cell phones, etc.

These (not sure I think) are used to build modified Roomba battery offered on roomba exchange and Vic or ... not sure. These have a higher capacity so are better able to meet high power requirements of bots. Thus they should last longer and provide longer cleaning missions. However, they used to have some issues with fires and explosions, so there are some dangers related to overcharge and deep discharge conditions. These are prevented by a good quality control circuits which I think the modified roomba lithium pack has. So as long as control circuits are good then there are no problems and Lithium battery works great.

2) New Lithium like LiPosphate and LiManganese, etc.

I am guessing that Roomba will move to this type in the next 6xx generation. They have bit less capacity but are much more robust and safer. In particular, they handle huge loads without any damage. Thus reagrdless how hard your robot works the battery is fine. Also they last a long time. I saw tests on A123 cells that were abusive and after 1000 cycles cells still had 80% of the original capacity!!!! So clearly these are the best, ideal for any robot. These should remove most of the battery problems people experience today. However, nobody makes these batteries for 4xx and 5xx robots today.

HINT: Make a 4xx and/or 5xx battery using B&D VPX packs please :)

richnorto · Joined: 03 Sep 2007 Posts: 256

Not to say anything about the last few posts - more to add to the original! I have a roomba that has started to not dock. It still runs a LONG time (about an hour) But only turns yellow at about 56 minutes. It has not made it to the dock in weeks! It seems to have lost it's memory for run time. Is this weird?

SpikeFiend · Joined: 07 Jul 2008 Posts: 11

I'm going with NiCd's for my replacement batteries. They're about as obsolete as lead acid batteries (Read: Not obsolete, just specific applications).

NiCd's take lots of abuse, and since I suspect the roomba charger is grossly overcharging NiMH's, NiCd's would be more effective here.

NiMHs do NOT tolerate trickle charging or heat at all. Yet everytime I would take the robot off the charger the battery was warm... NiCd's however can handle a much higher trickle charge rate.

Quote: Considering high power requirements, robots need more than NiCd can deliver.
The 1.5/2.0A the roomba draws is not going to bother a 2400mAh NiCd. Model airplanes routinely draw 25-30A from NiCd's for more cycles than a Roomba lasts.

If the charger was actually working properly, I'd say NiMH would be a great choice, but this isn't the case. You might actually get the rated number of cycles out of you NiCd's (500-1000 cycles) since they can take the heat (actually they are endothermic during charging so they don't heat up until the very end).

BobPaul · Joined: 10 Jul 2008 Posts: 9

Are the yellow batteries I see on Ebay labeled APS, the NiCd batteries?

bob_ninja · Joined: 17 Apr 2006 Posts: 174

BobPaul wrote: Are the yellow batteries I see on Ebay labeled APS, the NiCd batteries?

As far as I know iRobot doesn't make any batteries using NiCd cells.
Therefore, either some other company makes them or it is a custom build.

bob_ninja · Joined: 17 Apr 2006 Posts: 174

SpikeFiend,
Well written. Perhaps I was bit harsh on NiCd.
NiMH don't like trickle charge for days, but then most run their bots every 1-2 days. Otherwise, in my case I use a timer and don't allow constant trickle charging.

I forget how much current bots draw, but imagine it is more than 2A when running on top of a carpet. Both wheels and brushes encounter much more resistence, so I suspect a higher load. Still in principle a 2.4Ah NiCd will handle up to 5A draw just fine.

The main problem is capacity. I am not aware of 2.4Ah sub-Cs, but then didn't look very hard. I suspect that capacity might be the absolute limit. As for their lifespan of 500+ cycles, I am not sure about that. The longest one lasted was a Ryobi drill pack, less than 100 cycles I think.

I just think there are better superior alternatives available today making NiCd obsolete.

Sure, 2.4Ah sub-C NiCd can support up to 2C = 5A
However, similar size A123 cell can handle 30C = 60A

Now 5A * 22V = 110W is not much power for a robot that has many parts parts needing power (min 3 electric motors, bunch of sensors, controller, etc.) So I would rather use a much more powerful A123 cells that can support 5A and 10A without beaking sweat.

In terms of capacity, 2.4Ah sub-C would be the abolute limit. And that is after couple of decades of development. Whereas new Li cells are known to have a higher energy density, for the same volume they would offer more energy. Plus they are bit lighter.

Meanwhile NiCd still has some issues, like the memory effect. Over time their capacity tends to drop due partial charge/discharge cycles. The only way to restore their capacity is place individual cells into a charger that can cycles them until the effect is removed. That means taking apart the pack and putting it back together afterwards. What a hassle!

Meanwhile NiMH and Lithium don't have memory issues, at least not as acute.

Sure NiCds do still work. I just don't see any point in skipping on newer better Lithium technology.

BobPaul · Joined: 10 Jul 2008 Posts: 9

I don't understand your answer Ninja....... not talking about iRobot batteries......... at least I don't think so.
I don't know who makes them, but my question is still open: are the Yellow batterries with APS label NiCd batteries?
Excuse my ignorance.
BobPaul
P.S. I am trying to verify the best battery to get...... looks like Li-ion better than NiMh and NiMh better than NiCd.
Thx.