[PLUG-TALK] Rechargeable NiMH Batteries Question

[Russell Senior]

>>>>> "Rich" == Rich Shepard <rshepard at appl-ecosys.com> writes:

Rich>    This is a question for all the electrical gurus here.  My clock
Rich> radio takes a pair of AAA batteries for backup when the house
Rich> electrical system goes off-line. A couple of weeks ago the unit
Rich> indicated the batteries needed to be replaced. I charged a pair of
Rich> NiMH rechargeable AAA batteries and put them in the clock
Rich> radio. The discharged battery icon continued to blink. So, I
Rich> recharged the batteries and found the same result.

Rich>    Replacing the NiMH batteries with alkaline, non-rechargeable
Rich> ones, turns off the icon, indicating that they're fully
Rich> charged. The NiMH batteries each read 1.39 or 1.40 volts so they
Rich> are fully charged.

Rich>    What might make the clock radio not recognize charged batteries
Rich> if they're NiMH and accept alkaline ones?

The normal voltage of a fresh alkaline cell is about 1.6V, which is higher
than a fully charged NiMH.  Also, NiMH are more likely to discharge over
time.  If the purpose is backup power, you are probably better off with
alkaline anyway.


-- 
Russell Senior, President
russell at personaltelco.net