James Sweet wrote:

So here's the question: what about this battery pack makes the
transformer heat up to the point it burns out? There doesn't seem to
be a short in the battery pack, just a few bad cells. . .I don't
understand why this gives the transformer such grief.


Sounds like a few of the cells are shorted, this is causing the battery pack
to draw more current and overheating the transformer. It's possible the
transformer is damaged now but it may be fine.


2. While I was messing with this issue, I needed a drill. I went to
Freight Harbour and bought a very cheap ($30) 18V cordless drill to
tide me over. The battery pack that comes with it is rated at ~19V. I
tested the output from the pack and it was 19.2V. However, the charger
that comes with it is rated at 24V (or it says so on the wall plug).
So I figured they buried a resistor in there somewhere. However, I
tested the output from the charger -- 24.1V. So here's the question:

Will using this 24V charger on the 19.2V pack damage the charger or the
battery pack? I understand that this is a really cheap drill, but how
can they in good conscience provide a mismatched charger/pack? Is it
because 24V transformers are so cheap?



NiCd batteries are charged with a constant current, the voltage from the
charger needs to be higher than the voltage of the battery in order to
charge them, so the high open circuit voltage of your charger is normal, it
should drop down to the battery voltage when the battery is connected.

Thanks to all who replied. This post especially answered both of my
questions on point. I don't know if I will attempt a replacement of
the bad cells in the pack. Probably more trouble than it is worth to
me, since I have poor soldering skills.

Cheers,

Ed.