Rebuilding a Roomba Battery for Less

[iMayne]

To wrap up Ni-MH battery, inside the Roomba / Scooba, continues to power the robot after a successful charge while if a Li-ion battery is used, its protective pcb will stop all current from reaching the robot? So the Roomba must always "see" voltage from the battery or else is says err 5?

[Twobeers]

I have 2 of each, irobot roomba & scooba. 3 of the packs are nfg. All the cells are no good. They lasted about 3 months longer than the warranty. I've been experimenting with Li-ion cells, specifically the 18650 cells. The robots work for about 45 minutes with these cells. This is not suprising since the cells are just a tad under 2,000mah. So I have ordered thru dhgate.com 20 pieces of the 26650 ultrafire 5000ma li-ion cells for $125 (free shipping). I will use the charging/protection circuit boards out of some dead Ryobi battery packs that I have lying around (I knew that I was hangin on them for some reason or other). Both scooba & roomba charge up to 22vdc or about 1.8vdc per cell. 14.4vdc is the nominal voltage of the original packs, not their operating voltage. NiMi batteries typically discharge down to .8v-.9v per cell or the entire pack 9.6v to 10.8vdc.
Both the 18650 & 26650 cells have the same charge/discharge characteristics. Discharge to 2.5v per cell & charge to 4.21vdc. So 4 Li-ion cells per pack. Charge to 18.84v and dischage to 10vdc. Close enough to work with out any internal mods to the scooba's & Roomba's and I can use the Ryobi chargers to charge the packs with just a little bit of soldering and minimul wiring. I anticipate approximately 90-120 minutes of run time.

[Koontzy]

With my current job I have access to all kind of battery (security device) with almost every shape possible 6, 12, 18 volt and almost every amp too)
I'm looking into it to find cheap replacement and also those battery are way cheaper than RC battery

[rush]

Has anyone ever bought a battery pack from Aliexpress?

It's quite cheap (~30 bucks), Ni-MH ones, but i`m not sure if the "battery protection board" is a good quality one...

What would be a better choice? Rebuild my battery pack from fresh Ni-MH using the original protection circuit or these random aliexpress battery packs?

My house is quite small, i dont mind about really good battery capacity...

[vic7767]

The only protection used in the stock Roomba battery is a 4 amp polyfuse along with a 10kohm NTC thermistor. What info does your vendor provide for protection.

[rush]

Vic, vendor doesn´t provide any information.
I'm afraid that they do not come with any protection.

Price is quite cheap... Here is the link:
http://www.aliexpress.com/item/Free-shi ... 99459.html

[vic7767]

Check this one out: http://www.amazon.com/Tenergy-Replaceme ... ba+battery

[rush]

Check this one out: http://www.amazon.com/Tenergy-Replaceme ... ba+battery

Wow! Great price! But Amazon does not ship directly to my country...

Vic, after an overnight charge, I've loaded the battery with a lamp @ 1.7A, voltage dropped immediately to 12.3v.
After 45 minutes I got 10.9v loaded and 16.1v unloaded.
Is my battery dead? My roomba doesn't walk even 1 meter and shuts down.

[vic7767]

Yes, your battery is suffering from one or more defective cells. With a 1.7 to 2 amp load the battery should only drop about 2 volts at the beginning of the load test. It is not advisable to go below 12 vdc during a load test.

[camshaft]

just looking battery hack options

so the ebay cells would be 6Ah ? to compair to the amazon pack >?

25.49
NiMH battery, 3.3Ah Capacity, 14.4V

http://www.amazon.com/Tenergy-Replaceme ... ba+battery

24.30
6000mAh Sub C rechargeable Battery
http://www.ebay.ca/itm/14x-Sub-C-SubC-W ... 738wt_1397

[vic7767]

When you are looking at sub-c cells above 4500 mAH, be careful. Some are oversize and 12 of them won't fit into the stock Roomba battery case.

[camshaft]

Thanks

* Size: 4.3 x 2.3 (CM)
Have to measure old ones , great into

[camshaft]

the OEM ones are
43.7x22.4

ebay ones are Size: 4.3 x 2.3 (CM)

seem the same to me

[vic7767]

Grab up the deal and see how they run. Post back with your run time results.

[robj]

Hi all,

I've just rebuilt my Discovery battery using eight 4250 mAH 'ultrafire' 18650 style tagged / protected lithium cells.
(Edit - 400 series style battery for reference).

Having seen all the warnings about lithium battery charging & equalising problems, I also found a charge controller board on ebay that provides overcharge & overdischarge protection as well as cell equalisation.

The cells were supplied in pairs in shrink wrap, so I used each of these as a parallel pair on the basis the ones closest together out of the production line would probably be best matched.

I soldered each pair rigidly together with the tags angled in so they were just touching and used reasonably heavy link wires to chain the four pairs together.

They fit perfectly in the battery casing, I put both 2x2 sets in with the tags underneath to keep them away from each other. there is plenty of space over the cells for the (tiny) controller board.

The one I got is based on a Seiko S2854 controller and has power FETs rated at 8A continuous.

I refitted the original thermistor between the controller and cells.

The result is an 8.5AH battery which is, in theory at least, fully protected against overcharge, undevoltage and cell imbalance etc., at a total cost of (UK Pounds) £35

(You could just use four of these cells and still get 4AH+, or eight cheaper, lower capacity ones).

I've only used it for a couple of days so far, but it appears to be behaving OK.


If anyone is interested I can pull it apart & take some photos to show the details.
I can also post the exact batteries and controller if appropriate - I'm not sure about links to 'adverts' on here..

Robert.

[camshaft]

again I used
http://www.ebay.ca/itm/14x-Sub-C-SubC-W ... 738wt_1397

[supradupafast]

again I used
http://www.ebay.ca/itm/14x-Sub-C-SubC-W ... 738wt_1397

How have these been performing ? I need to rebuild quite a few packs, and am looking for some Sub C's.

[robhu]

Someone kindly gave me a Roomba Discovery but said that the battery was dead and that I'd need a US->UK voltage converter.

I bought the same batteries as camshaft, soldered them together and put them in... and it worked! But when I set it to charge the docked (and sometimes power) lights on the dock flickered and it didn't charge at all

I had a US->UK voltage converter from when I had a Discovery a long time ago which worked then, but from Googling I thought the flickering could be caused by the voltage converter not being up to the task, so I bought another this morning and the same thing happens :-/

Not sure what to do now... should I replace the dock or the charger or get new batteries, or what?

[robhu]

I realised earlier that the charger can be plugged directly in to the Roomba, I don't need the dock. It's been like that for about an hour now and what happens is after a while the power light glows red but at it's peak brightness it goes dark again, then after some number of seconds (which is random, it's not the same number of seconds each time) it starts again. As I haven't charged a Roomba for many years I can't remember what it's meant to look like when it's happening, but this isn't right, is it?

After an hour 'charging' it still won't turn on when disconnected from the charger I tried the battery reset procedure about half way through and that didn't help either.

Any ideas?

[vic7767]

The charging status LED should be on and pulsing amber and eventually go green after a few hours. From your description it would appear your Roomba may have charging system issues as well as possibly power supply problems. Have you measured the output voltage from the power supply ? What voltage is in the battery ?