Posts: 1,162
Threads: 26
Joined: Aug 2005
No, DON'T use a car battery. The short-circuit current of a car battery is somewhere around 1000A (!) and the risk of the NiCd exploding is fairly high.
I normally use my bench PSU (which has an adjustable current limiter), with the voltage control set to about 3V. Try it with a 2A limit first, if that does no good, try 5A, then 10A. If 10A won't clear the short then you need a new cell.
And only connect the bench PSU briefly. I normally clip one lead onto the appropriate side of the cell and just 'flash' the other lead onto the other terminal. Do this to one cell at a time (i.e. take the pack apart), you can't do several cells in series.
My experience suggests that cells that have once been internally shorted are damaged inside (probably the separators get damaged) and are likely to short again. I'll try to recover a cell to make sure the device it's used in works (and that it's worth buying some new cells for it), but if I intend to use said device
then I replace all the cells.