I had a pair of Atlas Copco/Millwaukee 18v NiCad batteries re-built about 15 years ago. I believe the company that did it for me used Panasonic cells in them, and they certainly had a much longer life than the original cells did. In fact, the batteries still take a charge now and the drills still work, but if I dont use the drill for a week, then I have to recharge.
At that time, the cost of buying a pair of new batteries was more than twice the cost of having them rebuilt with, what was technically, a better battery cell.
I would have had a few more done as the years have passed, but the company that did it used to be fairly local to me but I believe they relocated up North somewhere....????
Personally, I would recommend looking into this option. From memory, they used to have the common makes and sizes in stock and you just give them your old battery packs and they give you new, rebuilt ones.
I can remember the name of the company and hopefully they are still going and if its ok with the Mods...????
They are called Combat Alexander.
Here's a link
http://www.combatalexander.co.uk/main/m ... eries-home
There is no mention of power tool batteries on the home page, but give them a call and see what they say.
Tim.