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Can I substitute a NiMH battery for NiCd in a cordless phone?

M

Mark W. Lund, PhD

I don't know where Panasonic is coming from on this, but most
battery manufacturers are OK with trickle charging, indeed
most of the cycle-life tests are done with a 13 to 16 hour
trickle charge.

It might be that Panasonic is trying to cover up for the fact
that NiMH cells _do_ have "memory" and are trying to keep people
from seeing it.

Leaving the packs on a C/10 trickle charge for weeks on end will
cause a voltage depression "memory" effect just like NiCads.

The oxygen recycling mechanism from NiCads works just as good or
better with NiMH, trickle charging is OK.

Best regards
mark

Wolfgang said:
NiMH's do not like trickle charge, see ..

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NIMH_Precautions.pdf


and this is what happens in most simple devices like phones etc.

/WK

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting
 
M

Mark W. Lund, PhD

I agree with everything you say, but a lot of people call
the C/10 charge a trickle charge. Right or wrong, jargon
isn't locked down.

Best regards
mark

Doug said:
| I don't know where Panasonic is coming from on this, but most
| battery manufacturers are OK with trickle charging, indeed
| most of the cycle-life tests are done with a 13 to 16 hour
| trickle charge.
|
| It might be that Panasonic is trying to cover up for the fact
| that NiMH cells _do_ have "memory" and are trying to keep people
| from seeing it.
|
| Leaving the packs on a C/10 trickle charge for weeks on end will
| cause a voltage depression "memory" effect just like NiCads.
|
| The oxygen recycling mechanism from NiCads works just as good or
| better with NiMH, trickle charging is OK.

C/10 is not a trickle charge -- it's much faster than a tricke charge.

It's a slow charge, mind you, but a trickle charge is a good deal
slower.

Lots of people do seem to confuse C/10 with a trickle charge, however.

A `trickle charge' is defined as `An electric charge supplied to a
storage battery at a continuous low rate to keep it fully charged' and
for a NiMH cell that's probably around C/50, and for a NiCd it's even
slower.

Neither NiCd nor NiMH cells like being charged at C/10 day in and day
out. They may last a few months, and the NiCd cells will suffer
voltage depression (which is often mistakenly called `memory') and I
suspect that the NiMH cells will do, but to a lesser degree. But a
few days of C/10 won't hurt it, and in fact about 20 hours of C/10 is
pretty important for `forming' a NiCd or NiMH cell when it's brand
new.

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting
 
J

JM

quoting
NiMH's do not like trickle charge, see ..

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NIMH_Pr ecautions.pdf

and this is what happens in most simple devices like phones etc.

/WK


Though the ready made NiMh cardless packs are spec'd for this kind of
service. They can take constant trickle charging much better than standard
batteries. So as long as the OP gets one of these, he'll be ok.

There is always a trade off. The trade off with these batteries is lower
capacity than standard NiMh. Just look at the capacity: The lower capacity
is a dead give away, though it's still more than double than a standard NiCad
pack.
 
J

John Savage

It's about 2 years since I replaced the NiCd pack in my cordless phone
handset with NiMH. No problems so far. The phone is one of the older types
and probably about 6 years old.
 
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