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Saturday, September 8, 2007

Batteries, batteries, from everything.

John of TeamDroid sent me a link to this article about modifying and using the DeWalt 36v packs.

That's exactly the battery pack I've been looking at converting, for pretty much the same reasons it seems everyone else wants to do so.

I had wanted to use it as-is, so I could use it's ruggedized casing to hold everything, quick moutning points, etc, but it looks like it still has to come apart to have the charging/etc module removed if I need some higher current capabilities than it's designed for. I'm going to try to not need that much current from one battery, and instead use multiples, so that I can use it's own charge/discharge cutoff electronics to do my dirty work for me, but I'm not sure if it will work.

There is some really good info about some reverse-engineering done on the battery packs in the links from that article, and I'll be studying that to see if I can link into the existing stuff or have to bypass it all, which I'd like to avoid.

Originally, I had wanted to use some of the dozens of old laptop Li-Ion batteries I have around here, saved from the scrapheap when people replaced them because they didn't last as long as they used to, but still had significant life in the. Many of them are pretty old, though, and probably aren't worth even opening up to test the cells. Another problem is designing monitoring and control circuits so I don't blow myself up with these little cells, as they're fairly sensitive to overcharging and overcurrent draw for sustained periods. Ah, I had a great plan, though it is not really practical because of the charging controller issue--it's just not worth dealing with that kind of safety problems, especially not down between my legs in the main bike frame, where I'd planned to put them. :-)

Using the DeWalt packs with their integrated controllers will help me bypass a bunch of problems with the whole battery-design issue.

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