NTLK Re: Will using AC lenghten NiMH pack's lifespan?

From: Stainless Steel Rat (ratinox@peorth.gweep.net)
Date: Thu Aug 24 2000 - 13:28:56 CDT

* Bradley Smith <BradleyS@artisansw.com> on Thu, 24 Aug 2000
| 1. "The problem with the modern NiCd battery is not so much the cyclic
| memory but the effects of crystalline formation."

I've been saying this all along.

| 2. "When the *memory phenomenon* occurs, the crystals grow and drastically
| reduce the surface area."

>From the Battery FAQ:
> (from now on when memory is mentioned we refer to crystalline formation.)

I just refuse to call it "memory" because it isn't.

> It is neither necessary, nor advisable, to discharge a NiCd before each
> charge because excessive cycling puts extra strain on the battery. An
> analogy can be drawn with a hand towel which, by washing after each use,
> would wear out its fabric too quickly. It is, however, necessary to clean
> the towel on a periodic basis.

| yes, agreed. They are worn or damaged because you recharged them before they
| were fully discharged and thus you are experiencing a memory effect.

It is not possible for an electronic device that uses batteries, like your
Newton, to fully drain a NiCd or NiMH cell. Given a Newton device, cells
are required to provide at least 1.2V each. NiMH and NiCd cells provide
~1.25V, alkalines ~1.5V. When voltage drops to ~1.1V, the device shuts off
because the cells cannot provide sufficient power. As the FAQ states, you
need to drain the cell to 0.6 or lower to recondition the cell. This
requires a separate conditioner or conditioning charger.

Now, what is more likely is that you keep "topping off" the cells. That
results in an overcharge, which causes the paste in the cells to dry out.
That cannot be repaired. The only way to deal with that is not do it in
the first place.

Rat <ratinox@peorth.gweep.net>    \ Warning: pregnant women, the elderly, and
Minion of Nathan - Nathan says Hi! \ children under 10 should avoid prolonged
PGP Key: at a key server near you!  \ exposure to Happy Fun Ball.

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