Timothy Murphy wrote in message ...

(2) If so, where can one get a charger
that switches off when the battery is charged?

places that sell battery chargers? Look for a multistage charging one.

(3) How can one tell with a multimeter if a battery is charged?
Can one tell from the voltage?
If so, at what voltage would one say the battery needed charging?

yes, though it does depend. For small household cells and carbon zincs
(which can indeed be recharged), an analogue meter on 10A range, touch
the tips on the battery /very/ momentarily, and speed of needle
movement indicates charge. Fast = full, sluggish = empty.

Also a 1.5v cell delivering 1.2v off load is a bit of a giveaway.

Forlead acids you need more than a mulitmeter.


(4) Similarly, for non-rechargeable batteries,
can one tell from the voltage on a multimeter
if the battery should be thrown out,
and if so, what is the critical voltage for 1.5v batteries?

whatever voltage the appliance drops out of function at. If a carbon
cell is down to 1.4v off load, its not got much life left.


NT