8/29/2023 0 Comments Dewalt batteries rebuildIt had been off the charger for not more than an hour by the time I opened the case and got the cell ends exposed. I added a rubber band to keep the cells from flopping around. A thermistor was visible and taped in a hole in the fiberboard to make good contact with a central cell. The only thing holding the cells in formation is some thin fiberboard contact cemented over both ends of the cells. There was a small strip of black foam tape involved. Pushing on the terminals in the tower pressed the top cell out. Opening the case was no problem – six T10 screws came out easily, and the case split apart nicely. It was time to start doing cell testing, and that was the battery in the middle of the bench, so I tore that one apart. The battery terminal voltage was falling (which makes sense with the current increase), so I didn’t hold out much hope. As I checked in on it a few times, the current kept creeping up, so I’d turn the voltage down to get back to 200mA. Terminal voltage came up to 8V – maybe there’s a little hope! I put it back on to charge at 200mA (still with the 22 ohms) for maybe 15 or 20 hours. I ran a couple amps thru it for a few minutes (with a blast of maybe 5A for a few tens of seconds). Terminal voltage was about 3V – not good. I let it cook with about 0.25A for a couple of hours. I put a big power supply across it with 22 ohms in series. One pack came up “bad” (fast flashes of the charger’s one LED) every time I plugged it in, so I tried a more brute force approach. The DeWalt chargers seem to reset when you remove the battery, and I put each one into a charger a couple of times to get as much into them as I could. I started charging up the packs for cell testing. I’ve had them for maybe a year, so it was time to get moving.Īll 4 packs read much less than 1V as I started the project yesterday (last Saturday). In addition to Ed’s donations, Mike D from where I used to work gave me some old DeWalt batteries suitable for recycling. What better birthday gift for my friend Ed than a handmade rebuilt 18V DeWalt battery made from recycled sub-C cells? OK, especially when he provided 2 of the old packs I scavenged from.
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