charging NiMH vs NiCad

[Brian O]

Is there much difference in the way these batteries should be charged? I
have a portable radio that has a charger that tricklecharges NiCads, D
cells. Could NiMH be used in place of the NiCads without chance of damage
to the cells or to the radio? Any help is appreciated. Thanks.
B

 

[JeffM]

Is there much difference in the way these batteries should be charged?

Brian O

Google is your friend.
http://groups.google.com/groups/sea...NiCd+charge+OR+charger+OR+charging+OR+charged

 

[Brian O]

Google is your friend.

http://groups.google.com/groups/sea...NiCd+charge+OR+charger+OR+charging+OR+charged

Thanks for the link. I found an answer that makes sense, unlike some of the
help that was offered in here....

"Asking about the difference between NiCd & NiMH battery chargers -


The Cadex site (www.cadex.com) says that there are important
differences between the chargers. They claim that:


The charge termination criterion is different. Most NiCd chargers
stop (or transition to trickle charge) on a characteristic voltage
drop. The NiMH voltage drop is more subtle. Most NiMH chargers
transition based on temperature.


The NiMH cell requires a smaller trickle charge. "A trickle
charge that is acceptable for the NiCd will overheat the NiMH and
cause irreversible damage."

 

[CWatters]

Is there much difference in the way these batteries should be charged? I
have a portable radio that has a charger that tricklecharges NiCads, D
cells. Could NiMH be used in place of the NiCads without chance of damage
to the cells or to the radio? Any help is appreciated. Thanks.
B

The answer is only "possibly".

How do you tell if a nicad is full...well the voltage drops ever so
slightly. Many chargers look for this drop and switch off. If that fails
they have a safety timer as a backup. NiMH cells have a much smaller voltage
drop and the a NiCad charger can fail to detect it. In a fast charger this
can result in the cells being over charged and damaged (a fire even). In a
trickle charger the safety timer may or may be triggered before the cells
are charged.

So in your case the most likely outcomes are either:

a) It all works ok
b) The cells are overcharged, get a bit warm/hot and their life may be
shortened.
c) The cells may never be fully charged because the safety timer kicks in.

If you house burns down - remember that I recommend you buy a charger
designed for NiMH cells. They aren't very expensive and sometimes come with
free cells.