Ok, so I have a battery powered electric drill. Years old and so are the Nicad battery packs. One wouldn't charge at all, and the other wouldn't hold a charge. I thought about making some new packs, but did a bit of research. Over the years the internals of Nicads become crusted up and they stop transmitting or accepting current.
To revitalise them get a car battery charger, and tap the crocodile clips against the +/- on the battery, but only briefly. Do this a few times, you will see sparks but that's ok. What you are doing is shoving a high current through the Nicad that blows the crud off the internals. Do not hold the charger clips against the battery, just tap them.
For tank batteries you may need to make up a lead from the Tamiya plug, just make sure that any bare ends cannot touch. Just clamp them into a block connector, and put two nails in the charger clips.
I did this on the drill batteries, and bingo, fully functional Nicads again, and they are a good 6 years old. One was down on 3.5v and wouldn't take a charge. I did this trick and put a multimeter on afterwards. The voltage steadily rose from 3.5v to over 5v while I watched. Put it back in the charger and it took a full charge again.
Just saved myself over £30 on new battery packs.
Rob
