The Natural Philosopher wrote:
Fred wrote:

"BigWallop" wrote in message
...

NIckel Metal Hydride Batteries need a low, slow charge ...........


That means my 2 hr charger is no good then


Not necessarily.

Fast chargers for Nicad and NiMh exist, that look for a drop in cell
voltage signifying end of charge. The acceptable 'fast charge' rate
for
NiMh with a GOOD delta-peak xcharger is one hour, and 20 minutes for
Nicad. Needless to say I have done a full Nicad charge in 12 minutes
many times, so these are conservative figures.

Charging NiMh faster than one hour tho leads to reduced capacity
eventually and poor lifetimes.

The voltage peak on NiMh is also much smaller than Nicad, which means
the chargers AND THE WIRING TO THE BATTERIES needs to be of good
quality.


I have to say, these batteries are hopeless if you charge them and
expect to use them in 2 weeks time. They'll be flat.

Yes, that is NiMh to a T. I've bitten the bullet and gone straight
from trusty NiMh to Lithium Polymer. Buit then, my requirements ae
more specialised...you are still stuck with a one hour charge, but
the charge
life is in months, not dauys, and teh energu density is far higher...

Fast charging for NiCd should stop when the terminal voltage peaks then
declines. For NiMH, charging should stop when this voltage peaks. The
better chargers will also monitor battery temperature. Although NiMH cells
tend to lose charge faster, the higher capacity and lack of 'memory' effect
more than compensate - the cells can be topped up at any time. Charge life
can be extended by storing in a 'fridge.

The following site has some useful information: http://tinyurl.com/ykku

Terry D.