Peter Parry wrote:
snip
As an aside the "chargers" supplied with cheap electric drills are
the worst of both worlds. They are unregulated and usually charge at
about one quarter of the batteries capacity. This gives a charge
time of about 5 hours, too long to be useful but with a charge
current far too high to be maintained for more than 5 hours without
causing damage. Leaving one of these batteries on charge overnight
once is usually enough to damage it irreparably.

If you have a electronic thermometer, with an alarm, this can be a good
use for it.
Simply stick on top of the battery to be charged, with a foam scrubbing
pad (insulation) and a small weight to keep it there, and turn it off
when it beeps (at room temp +5C)