RE: [OM] NiCd vs. NiMH OT

Subject: RE: [OM] NiCd vs. NiMH OT
From: Chip Stratton <cstrat@xxxxxxxxxx>
Date: Sun, 12 Nov 2000 21:12:21 -0600
I suspect the most important factor in life of NiCad and NiMH cells is the
quality of charging they get. Most probably die from overcharging, not
'memory' effect. And the slower the charge, the more cycles you will get out
of them - which should be about 500.

The most sophisticated chargers are microprocessor controlled and monitor
battery voltage, temperature, and charging time to arrive at a proper charge
and avoid over-charging. Surprisingly, these kinds of chargers aren't
horribly expensive if you know where to find them.

The other fast way to kill a rechargeable cell is to reverse charge it.
Obviously, putting a fully discharged cell into a charger backwards will do
it, but that isn't the most common way to reverse charge and damage a cell.
Rechargeable cells are almost always used in series with other cells,
forming a battery. If one cell runs out well before the rest of the cells,
and you continue to use the battery pack, that weak one will be reverse
charged and become even weaker next time around.

Bottom line is you need to treat your rechargeables with as much care as
your Zuikos if you want to get maximum use of them.

Chip Stratton

> I'm looking to buy, but I am not sure which way to go. I've had NiCads
> before, but they didn't seem to last. Cost aside, I'd like to get a handle
> on:
> 1. shelf life when charged
> 2. which lasts longer, assuming equal mh per cell
> 3. recharge time
> 4. number of battery charge cycles in a lifetime
> 5. memory effect
> 6. tolerance of over charge
> 7. tolerance of infrequent use
> 8. do they both load the electronic flash capacitor at the same rate
> 9. safety (oly 600dl specifically recommends against NiMH due to heat
> concerns)

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