Cordless power tool battery replacements are expensive: you can easily spend $100 for a NiCd pack. [henal] decided to skip nickle-based cells and cut out the middleman by converting his old cordless battery packs to inexpensive hobby lithium cells. These batteries appear to be Turnigy 3S 1300mAh’s from Hobbyking, which for around $10 is a great bargain. As we’ve explained before, lithium batteries offer several advantages over NiMH and NiCd cells, but such a high energy density has drawbacks that should be feared and respected, despite some dismissive commenters. Please educate yourself if you’ve never worked with lithium cells.
[henal] gutted his dead battery packs and then proceeded to prepare the lithium replacements by soldering them to the cordless pack’s power connectors. To keep charging simple, he also branched off a deans connector from power and ground. After cutting some holes in the pack for access to the balancing connector and deans connector, [helan] went the extra mile by soldering on a DIN connector to the balancing wires, which he then securely glued to the side of the case.
We’ve featured lithium power tool replacements before, and these Turnigy packs pose the same problem: they don’t appear to have any low voltage cut-off protection. Check out some of the comments for a good solution.