Rebuilding a Roomba Battery for Less

[bstone]

Hey folks. I am wanting to wire my own NiMH Sub C using these batteries: http://www.all-battery.com/sc5000mahhig ... ttery.aspx

Is this a good choice for Sub C NiMH batteries? The 5000mAh seems very high and would be a good choice.

I look forward to your replies.

[vic7767]

At over $7 a cell you will be building a very expensive Roomba battery solution. 5000mAH is a little overkill but to each his own. The only issue may be the brand name. Lots of folks have not been happy with the performance of other Tenergy cell that they bought and built Roomba batteries with.

Give em a try and post back with your results.

[bstone]

5000mAh is a lot, and it's expensive.

I am considering purchasing this: http://www.amazon.com/Generic-Replaceme ... roduct_top

In the comments, many people reported receiving 3400 or 3800mAh cells instead of the 2400mAh. I wrote to them asking what cells they are using. If it's the 3400 or 3800 I'll surely be purchasing it.

[Mibars]

Hello from Poland!

We've just recieved out xmas present - Roomba 400 and while googling more informations about it I found this page. I see that some people alredy tried rebuilding batteries with 12x AA with mixed results (low running times because of lower capacity and high cell and battery cases resistances) and I've just measured orginal battery case - and it's exterior size will fit even 24 AA's. Battery box will need to be modified (cutting a hole on top and wrapping it with duct tape to increase usable height) but you'll end up with high capacity (use 2,7Ah cells like GP, Energizer, etc to get 5,4Ah battery pack!), high current (2x 12 cells parrarel) and medium priced (24 brand name Ni-MH aren't that cheap) battery pack that should do it's work - probably better, than this original hi-cap 3,5Ah pack.

It's just theory, since our Roomba is less than one week old I'm not going to do this until battery wears out Maybe someone has an old battery pack, manual skills to modify and solder battery pack and some free time to check this 24 AA pack out?

[mfortuna]

One problem I see with this is by increasing the height of the pack gives you less ground clearance. Also the more cells you have, the more problems you have with cell matching and reverse charging.

[Mibars]

Another idea: Using parts from 8-cell 14,4V-14,8V laptop battery with it's BMS inside Roombas battery box? Cells are usually 18650 (18mm diameter, 65mm lenght) so they should fit inside in two 4-cell banks, board with BMS isn't that big and should fit anywhere inside. Anyone tried this?

[blackest_knight]

Decided to start refurbing my roomba and i've bought a 14.4 volt drill for €17 its NiCd 1200mA cells so might be a bit short on run time. Just soldered them up and it's charging now. However for the price its probably as cheap as I can get, buying cells was going to be around €50 to get it running again. Seems to be very few european sellers of the battery pack and postage gets quite silly even then. I'd be stung for import duty if I go for an american supplier.
Battery pack seems to be glued and screwed. I ground up a cheap driver to make a cheap triangle drive

[sageman]

i got a roomba 400 battery for £27 and its 3.5AH the price included postage

[Madgardener]

After rabidly reading all the posts over the last couple weeks, I decided to take the plunge and register. This is a might interesting chat going on here about the Roomba batteries. As the proud owner of a Roomba Sage, a 563, and dirt dog (currently not working). I have built up a rather large stack of batteries to rebuild.

I'm having fun with this project, but one question that I have not had good luck solving in any other way is that I can't find out what model the varistor in the battery pack is. Does anyone know what it is and where I can buy a replacement?

Thanks.

[Gordon]

... what model the varistor in the battery pack is.

Think thermistor, not "varistor".

Does anyone know what it is and where I can buy a replacement? ...

AFAIK, the exact thermistor has not been identified. Perhaps you can use the data contained in this thread to source a likely candidate: viewtopic.php?f=4&t=12750

That thread's OP refers to Roomba-500 series (a.k.a., "R3") thermistor data, but all former Roombas have used the same nominal thermistor in their batteries.

Generally speaking, it is possible to harvest the thermistor from the old pack that is being replaced.

If your replacement pack does not come with an in-line fuse assembled to it, you need also be concerned about fusing the pack. A polymer (auto resetting) type is used, and is, I think, procurable in piece-part form.

[vic7767]

Here is the part number for a 10k thermistor (NTC type) from Mouser.com

71-01M1002KF

[Madgardener]

Thanks for the info. It shall be put to good use. I wasn't sure about reusing electronic components, but if they can be harvested and reused, so much the better. For such a tiny device, the thermistor seems pricey.

[vic7767]

There are other thermistors that cost less, the one mentioned is an example of what is needed.

[Madgardener]

The rebuild was successful, my Roomba sage is purring happily on its new battery pack. I took apart a third party battery pack that I bought about 14-16 months ago from Ebay (Batterygeek1) and replaced the cells in it. A little bit of soldering and it works great.

Now to replace the batteries in my father-in-laws 18v Ryobi battery packs.

[slippa]

Hi All

I just picked up 2 Discovery XE's + chargers and virtual walls for £10 at a car boot sale. The batteries are both shot so I've just bought an official battery off Ebay and confirmed that both units work. I would like to build another battery using the batteries in the link below. Can someone with more experience in these things please let me know if these will do the job. I thought I'd buy 14 in case any of them are dud.

http://www.ebay.co.uk/itm/14-X-Sub-C-Su ... 2eb713885c

Any advice you can provide would be greatly appreciated.

Many thanks
Slippa

[vic7767]

Since I no longer get along with ebay I didn't look at your URL, however all you need is either a drop in kit for the Roomba or build your own by looking for Sub-C cells with at least a 2100-2200 mAH capacity or higher. If you decide to build your own pack using 12 Sub-C cells you can salvage the resettable fuse and thermistor from a defective Roomba battery.

[slippa]

Thanks vic7767
These are
14 X Sub C Subc 6000mAh 1.2V Ni-MH Recharge Battery Tab for £15.78 inc delivery which seems like a good deal to me. i've identified the fuse and thermistor in one of my spare batteries so I think I'm good to go. The only question I have is the thickness of wire I should use to connect the individual cells and whether these cells will be fine to charge using the roomba itself or the docking station.

Many thanks
Slippa

[vic7767]

I use 24 gauge solid copper wire. It would appear that most of your connections will be using the tabs that are already attached to each battery. The battery will be able to be charged using both the stock power supply as well as the home base accessory.

[Prof. Prevaricador]

Hi!

I already finished my 14 X Sub C Subc 6000mAh 1.2V Ni-MH Battery but I didn't installed the fuse and thermistor isn't glued to the cell like the original battery...

How does the roomba know that it is already charged? Is it using the thermistor? I've read that some chargers read the temperature to know hwen to stop charging...

I run the roomba with just the power from the batteries and it cleaned for about 20 minutes until it fully discharged.

Next I charged the roomba in the home base for nearly 2 hours until it got green and the roomba cleaned for 1 hour.

The following days it charged for 1 hour until getting green and cleaned for 1 hour until it fully discharged.

To you think it's charging too rapidly? How about the run time? Shouldn't it run longer being a 14 X Sub C Subc 6000mAh 1.2V Ni-MH Battery?

Thank you all

[vic7767]

If you have built a Roomba battery with 12 sub-c cells with 6000 mAh capacity then the robot should be running at least 3 hours. The Roomba charging program utilizes voltage and current sampling as well as termperature to determine when to lower the charging current.