Rebuild Battery Packs?

[Pat Barry]

I need to get a new backup 12V NiMH battery for my trusty Makita drill. I recently bought a replacement at HD for around $55.00. Now wondering if I couldn't take the old one apart and replace the cells for less money. Does anyone here have any experience doing this? Is it worth it? Also thinking about whether I would be able to convert this to Lithium Ion?? Appreciate you thoughts.

[Gil Knowles]

Pat
I have not rebuilt any batteries yet but am planning to. I found this site with some good information on rebuilding.

http://www.astromart.com/articles/article.asp?article_id=587

Gil

[Brian Vaughn]

Whatever you do, do NOT try to rebuild with Lithium Ion. LI is very temperamental, and charging it (or discharging it!) at the wrong rate can ruin the battery, or in a worse case, cause it to explode. The actual rebuilding of a battery like that is a simple thing to do. Many places sell cells, once you get it open and see what size cell is inside. However, that's typically the difficult part (Getting into the battery portion and not ruining the outer case). The actual act of making a battery pack is a simple thing, I used to do it all the time (I fly RC planes, and we use all manner of battery cell combinations). One of the other critical things to remember, though, is to be careful when soldering your new pack together. Getting the battery too hot can cause all sorts of fun effects.

Also, unlike that article, which is a decent overview, I would say to go ahead and replace all the cells. Those cells are typically relatively cheap, and if you're going to go through the effort to break it open, you might as well make it like new. Besides, those cells will slowly lose their ability to charge, the more they are used. So if you're combining new cells with old cells, it's just going to put more stress on the new cells and cause them to fail sooner.

Oh, and I don't care what he says, modern NiCD's do still have a memory effect. It's a byproduct of the chemistry, and nothing can change that.

[Brian Vaughn]

I read my response, and let me clarify something. Li is a very great battery, however, you need to use a charger and a tool that's made to work at the proper voltage/amperage for the lithium battery. If you try and use a Li battery on a NiCD or NiMH tool, you could experience an explosive decompression, just as you might in a NiMH or NiCD charger.

[Pat Barry]

Yeah, Brian, I was thinking I might need a new charger if I switched - that might be more trouble than I was looking for. My existing old battery just doesn't charge up anymore - I was thinking that I would need to replace all the cells. Thanks for the input, and Gil, Thanks for the link.

[Bruce Wrenn]

Contact Jason over at MTO Batteries for a price to do a complete rebuild. Many here have used his services.

[Mike Hutchison]

Batteries Plus has rebuilt Ryobi battery packs for me in the past.
Generally happy with their service on this and computer related items.

[Jim Andrew]

I dropped one of my Makita nimh batteries. It will not recharge now. Does this mean I might take it apart and repair it?