No prob, just add a couple well placed heat sinks and a muffin fan and.
#REPAIR A 18 VOLT DEWALT BATTERY PC#
OK, some creative PC board work, lots of electrical and duct tape and.hold on.this thing is getting really hot. To regulate it down to 12VDC, it took a chunky bridge rectifier, a few big filter capacitors (think 35mm film capsules) and a pair of high end MOSFETS along with some IC chips and and a handful of other bits to build a PWM controller. I pulled from the center tap, thus 12VAC, but it too was unregulated and actually put out just under 18VAC. In order to get the necessary amps to make some real torque, I had to use a huge 24VDC transformer rated for 35 amps. Sure, it's not a regulated supply, and the amps are barely enough to spin the drill, but at least it fits inside the stock DeWalt battery case and best of all, no smoke. Making 12VDC from 120AC is easy, a small transformer, a rectifier, capacitor and a few other bits and wha-lah. You'd think (and maybe someone has) someone would invent a battery shaped adapter with a power cord sticking out, so in the worst case scenereo you could just plug it in.I played around with your idea (and it's a really great one) and the result was a 9 lb "anchor" duct taped to my cordless drill. Essentially I was only working with 4.5v of power. For my 12v Dewalts (9 - 1.5v cells) having 3 bad cells each, it meant that I wasn't even getting the benefit of the remaining 6 good cells, because they were giving up their charge to the the three bad cells with reversed polarity. If a battery pack is allowed to go very dead, the cells holding a higher charge will actually start recharging the weakest cells and reverse the polarity of those cells. who likes fixing things, it wasnt so bad. I just ressurected a pair of 12v DeWalt batteries ($56 each new) for $9 in rechargable batteries and an afternoon of fussy work. Again, you will have to solder the leads back on. Be certain, when putting new cells back in, that the polarity is correct. You will probably have to cut or de-solder the leads going from cell to cell to be able to extract the bad cells. Mark the cell and keep checking the cells until you get to the end. From cell to cell you should see a 1.5v jump. Using a multimeter, check and make note of the voltage reading between that point and the negative end of that cell and then from the negative end of each cell in sequence. After your battery pack has been on the charger long enough, take the cover off the pack and identify the positive end of the first cell in the chain. These are available at Radioshack or any place that sells rechargable batteries. An 18 volt battery pack is made up with 12 "C" sized rechargable cells. It will take some doing, but you can repair cordless drill batteries.
Land o lakes, I posted this under the "Bad battery or bad charger?" thread, but it might help.
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