Rebuilding a Roomba Battery for Less

Inside the Roomba and Scooba and more, Cool mods, Repair and Upgrades - including the all new iRobot Create Kit. Let's void that warranty baby!

Postby Gordon » February 13th, 2006, 2:29 pm

Polarity is confirmed by looking at an old, black battery case on which (+) and (-) are marked. The (-) RTN-contact is closest to the cell-pack. Polarity did not change for the APS battery.
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battery comparison

Postby Derek » February 13th, 2006, 8:34 pm

anybody know the mAH diff between the APD and the preferrred hack from Batteryspace ( ) ?

Postby rj5555 » February 14th, 2006, 7:25 am

Original (Black) Battery = 2300mAh
Original (Yellow) APS Battery = 3000mAh
Batteryspace cells = 3000mAh (so the same as the yellow APS batteries)

If you want you can make your own cell pack using GP3700 or IB3800 or IB4200 cells (You can find them in RC car battery shops) giving you 3700mAh, 3800mAh or even 4200mAh
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Batteries cheaper on fleabay

Postby george2001 » February 15th, 2006, 9:00 pm

Oppps...that's me messing up trying to edit this post in the following post!
Last edited by george2001 on February 15th, 2006, 9:42 pm, edited 1 time in total.
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Re: Batteries cheaper on fleabay

Postby Guest » February 15th, 2006, 9:40 pm

I was looking around fleabay and found that there's someone selling the exact battery replacement found here:

But they're selling them for about $35 shipped, including the special triangular screwdreiver. The referenced site wants about $42 including shipping and the special triangular screwdriver. Just search for "Roomba battery".

Also, a 3300 MaH Roomba battery pack is available from Batteryspace for about $40 plus shipping here:

For us lazy folks, Amazon is selling new APC packs for $45 after applying discount code, free shipping, and no sales tax (at least in California).

Postby rovermaster » February 22nd, 2006, 6:12 am

Does anyone have more info about the varsistor? In the process of replacing my battery, a lapse of attention caused the pos and neg leads to touch. After I noticed the smoke eminating from the middle of the battery pack, I discovered the varsistor had completly burnt up. I now need to replace the varsistor as well as the batteries. Please provide any info available on the varsistor to help an attention deficient Roomba owner.

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Postby Gordon » February 24th, 2006, 3:36 pm

rovermaster wrote:Does anyone have more info about the varsistor?... After I noticed the smoke eminating from the middle of the battery pack, I discovered the varsistor had completly burnt up. ...
First, these batteries contain a "temperature-sensor", which behaves like a "thermistor", and a "fuse", which turns out to be a *resettable-fuse* using 'polymer' technology. No varistor, AFAIK.
If you contacted the (+) termnal to the (-) terminal, I expect the 'fuse' was subjected to more current than it could possibly "reset" from!
OTOH, if you contacted the (+) terminal to the *side-contact*, the thermistor (which could also be a 'polymer' device) would be destroyed. It has a negative temperature coefficient, so as heating continues, resistance goes lower. Was the smoked device embedded in the middle of the cells-pack? That would be the temp-sensor.
The fuse is located at the connector-end of the case.
I have data on the fuse used in the black-batteries, but don't know if the same part is in use in the APS batts. Here is a lead on the "LP30 | 400" fuse. I have a small text-file with other info about searching out the fuse data; let me know if you want that file.
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battery voltage

Postby metech101 » February 27th, 2006, 2:37 pm

if you use 12 c battiers, 1.5v each, then you have a power pack of 18v and you only need 14.4v. it looks like to me you only need 10 battiers?? why 12????

Re: battery voltage

Postby Guest » February 27th, 2006, 3:35 pm

metech101 wrote:if you use 12 c battiers, 1.5v each, then you have a power pack of 18v and you only need 14.4v. it looks like to me you only need 10 battiers?? why 12????
It looks to me like you need to learn about NiMH cells; they have a nominal 1.2 volt output, not "1.5v".

battery voltage

Postby metech101 » February 27th, 2006, 6:57 pm

thanks for battery info. jwp..

Postby anakin14 » March 16th, 2006, 10:33 pm

FYI: NiMH cells, when peaked, have about 1.25 volts. Their discharge curve is pretty flat. The cells are considered "drained" at 0.9 volts.
Check out my site!!
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Postby rovermaster » April 26th, 2006, 12:49 pm

Also, a 3300 MaH Roomba battery pack is available from Batteryspace for about $40 plus shipping here: ... rodID=2321

There is one very nice problem with the batteries found at the link above.

I upgraded the original APS battery in the Roomba about a week ago. Since I upgraded, my Roomba has been running for about 2 hours, 15 min before needing to be recharged. It now runs longer than the auto-off of the virtual walls. This is causing my Roomba to get stuck on the floor mats in my bathroom due to the fact that the virtual walls are shutting off too soon.

This is a problem that I am thrilled to have. Thanks for the link.
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Postby Axios » May 2nd, 2006, 1:07 pm

Ahem... :oops:

I did it.....

I bought the 3600 mah battery pack for the roomba.... My original battery (yellow one) has always been too lazy and it stopped working not too long ago... I suspect It was faulty because, as I said, it has never worked too welL.. now I bought the kit with the 3600 pack and the screwdriver... I hope to have the same gain I have read, because the Disco cleans very very well and I am not satisfied by letting it sleep idle too much... :wink:

I will post a little review of the upgrading process and, I hope, of the better performance ASAP!
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Is the yellow polymer fuse needed?

Postby g2lee » May 10th, 2006, 11:42 am

I just bought one of those 3300 mAh kits off of eBay and it doesn't have that yellow polymer fuse attached to the red wire like my original battery did. Is this needed?

The 1st time I recharged it in the rapid charger, the charger and battery got really hot after 3 hours and I was afraid it might overheat so I manually stopped the charging.

The 2nd time, it stopped recharging after 3 hours like it should.

Does the polymer fuse affect the automatic shut off of the charger?
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Anyone tried Li-Polys?

Postby makarov380 » June 8th, 2006, 8:17 pm

I play with model airplanes and it seems like Lipoly batteries could be used. They are similar to the Li-ion that were used earlier in this thread. They would require a special charger and all the warnings that go with LI-ion, but a pack should be lighter and have more capacity and a slightly higher voltage @ 14.8V. The one thing to be careful of is the amp draw- anyone know what the amp draw is for a Discovery?

I just ordered one to go with my new floors and St. Bernard so I am excited about the prospect of not cleaning everyday. Maybe when the warranty runs out I'll try the Li-po idea and see if I can double the battery capacity.
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Postby answerguy » December 29th, 2006, 10:43 am

Just in case it hasn't been mentioned in this thread a Torx 6 screwdriver fits that ---- triangle slot perfectly. Less than 2 bucks at Sears.
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Scooba battery too?

Postby CWW » January 13th, 2007, 11:42 am

Does this upgrade technology work with my blue Scooba battery?
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Re: Scooba battery too?

Postby davem » January 16th, 2007, 10:37 pm

CWW wrote:Does this upgrade technology work with my blue Scooba battery?

Not really.
The Scooba battery is similar in design but totally different in implementation.
It uses an arrangement of 12 batteries of a different size
called 4/3 AF, a new and somewhat obscure form factor.

See this recent thread
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Postby jaredrawk » January 29th, 2007, 1:34 am

-- TIPS for noobs --

OK, I just finished this surgery and I now have a Roomba Red running with much more life and dare I say pepp to boot.

HOWEVER I must say this procedure is not for the faint of heart. Unlike the times posted here, I took more than two hours starting from the much talked about Pre-assebled 4200 mAh battery pack: ... rodID=2321

Here are some notes from my experience.

1. the Yellow Advanced battery pack was far from easy to get open.

In fact this is where I spent an hour and a half. I ordered the special triangle screw driver and the screws backed out fine. But the top was glued tightly to the bottom. It took some time and a lot of patience to separate the two without breaking. I ended up with a flat jewelers screwdriver and punching it straight in for about 1/16 of an inch all the way around cracking the glue. It then took one punched in hole, a wood chisel and a lot of careful prying. It was a major pain and the battery pack is far from pretty. Though it did go back together.

By the time it was over with I was thinking, maybe some Bestine would have helped out... but then I also thought it is really flammable, so using it on a battery pack could yield disasterous results.

2. Work on a dead battery pack...

OK, OK, a lot of people are rolling their eyes right now and they should. But one or two are also nodding knowingly. You start this after all because your battery pack is dead. Not working well. So in your head you are convinced it is dead. And you havn't used your robot for a couple weeks now, and it is easy to forget the last thing you tried in your trouble shooting was charging the battery for a day. Now you see with all that prying you may eventually make contact with something... and at that moment a dead battery is better than one with any life at all.

3. Get one of those fancy cold steele soldering irons.

Batteries Plus stops just short of having a pre-assembled pack. They don't solder on the contacts. You have to do that. Having not soldered anything since college I had forgotten where my soldering iron was. What I did find was one of those nine dollar jobs I bought last time I lost my soldering iron. It sucked. It was not hot nor fast enough to do an effective job. But it was hot enough to burn my arm though.

4. Measure first, then cut.

The wires in the kit are thankfully much longer than they need to be, but of course if you just de-solder the contacts from the other battery pack and slap them on the new wires, you will be starting over when you try pack the battery pack back together, as all that extra length won't fit anywhere. You have to measure the wires to the contacts, snip strip and spark.

5. Your new battery will have juice.

See 2. After making the journey all the way from China, your new super battery will still have plenty of energy to shock the crap out of you. So be very careful as you put it back together.

6. In the words of the MythBusters, I did these things so you wouldn't have to.

If you have engineer in your title, especially Electrical or Mechanical, this project is probably childs play. If you are really good at taking things apart, but not so good at putting them back together, you might want to think twice. If you just want to have that 40% more life and are a bit spendthrift, forget it. In the end unless you can get really excited about the thought of prying apart plastic just buy a new battery pack... chances are somewhere before you get it back together, you'll be buying a new one anyway.

-- lates
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Repairing a Roomba battery

Postby mundt1 » January 31st, 2007, 2:32 pm

Hello jaredrawk,

I'm glad to see that you were successful in your battery replacement effort. Once you've done all the work to get the case open :) you might want to put in something better than NiMH batteries. Check out the information on the the Li-ion battery thread.

Opening an APS battery case is only difficult the first time you do it and don't know what to expect, or how it is held together. This proceedure works well for me and only takes about 5 minutes.
1. You need
- a reasonably sharp pocket knife
- two "normal" flat screw drivers
- a small hammer, or anything else you can tap on the knife with
- a special tringle screw driver or a modified 3/32" allen wrench (see below)
2. Remove the screws.
2. Lay the APS on its side on a flat, reasonably sturdy surface
3. Position the knife along the seam line. Starting at a corner works well for me. Use the blade, not the tip.
4. Tap knife sharply until you hear a "snap" (as the glue breaks) or until it is in ~1/16".
5. Move the knife along the seam and repeat, Use the tip as needed arround the end latches.
6. Once you have been all the way around the case seam, the lid is being held on by a few small posts or tabs on the inner edge of the case.
7. Insert a flat head screw driver into the seam near the center of the case. It's not necessry to insert it very deeply. Twist it slightly to open up the seam a little.
8. Insert the second flat head screw driver and slide it alond the seam as far as you can. Twist it to break or release the small glued tab.
9. Repeat all the way around the APS seam.
10. You should now be able to remove the battery case lid with a little more prying at any points still glued together.
11. The battery pack and the contacts can now be removed.
12. Reassembly is a little easier if you clean up (cut off) any of the small posts which may be sticking up.

A "special" triangle head screw removal tool can be made relatively easily from a 3/32" allen wrench. Simply file alternating faces of the 6 sided hex (file flat against the face) until the "unfiled" faces vanish and you are left with a triangle. Alternate filing the faces, removing a little at a time (2 or 3 file strokes). The alternating faces of the allen wrench are prealigned at the necessary 60 degree angles. The 3/32" wrench requires the least filing, anything larger requires filing past where the filed faces meet. Only a section of the wrench ~1/8" to 3/32" long needs to be filed.

I hope that this helps the next person opening an APS case.

Best of luck.
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