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Wayne Minami
01-19-2014, 11:53 AM
The control module in my Dewalt 28 volt LiPO4 battery is heating up.
The Background:
I have a nonfunctioning Dewalt 28 volt battery pack. Did not want to buy a "New" one since they stopped making these several years ago. So anything on the market is old already.
I tried 2 battery rebuilders and both said they did not work on this battery.
After reading a post I opened the pack, tested the 8 batteries, and found that only one was bad (the battery to which the thermister is connected).
Got online and ordered the single battery and installed it. I had to add and extension on one wire because it was too short. I used 18 gauge wire, soldered it, and covered with shrink wrap tubing.
I had 2 incidents where I mistakenly touched the terminal and the body of the battery with the soldering iron. After that, I covered the new battery with electrical tape.
When I reassembled the unit, the control module, for lack of a better term, got hot over the course of several minutes. The batteries remained cool to the touch.
I immediately took the unit apart, checked the work I had done, and reassembled. Same thing happened. Redid one solder joint, same result. I am experienced at soldering so think I have good joints. If I had a cold joint, there would be no current to the control unit.
My question is: has anyone else experienced this? I fear the battery pack may be a goner.
I would appreciate any insights.
Thank you.
Wayne

Ken Fitzgerald
01-19-2014, 11:58 AM
How difficult is it to disassemble the battery pack?

It's possible that another battery has or is shorting out when charging.

Can you wait until it heats up again and then quickly disassemble it and feel which one is hot? The warm/hot item should lead you to the problem.

Wayne Minami
01-19-2014, 12:12 PM
You need a Torx t10 tamper proof bit, which I got on Amazon to disassemble the pack. The only thing that is heating up is the control unit on top of the batteries. It is the part which connects with the tracksaw. The 8 batteries themselves are cool.

Wayne Minami
01-19-2014, 12:23 PM
Ken, sorry, I missed your last question.
i never fully assembled the pack. It has plastic covers at each end with the contacts built in. As soon as I put those covers on, completing the circuit, the control unit started to get hot. So there was no point in putting it back into the case, which is a very tight fit.
wayne