Re: [NTLK] NiMH and battery gauge

From: gopi_at_sin.sloth.org
Date: Mon Jul 09 2001 - 17:40:33 EDT


On Mon, 9 Jul 2001, Stainless Steel Rat wrote:
> * "Peter Cameron" <pdwcameron_at_hotmail.com> on Sun, 08 Jul 2001
> | I tried the Radio Shack 1600 mAh cells in my MP2100 and found they were
> | fine except if you use the backlight a lot or use a modem. They drain
> | quickly under heavy load and don't recover well. I'm having much better luck
> | (read longer battery life) with Radio Shack 1000 mAh NiCads.
> That is not suprising. Ni-Cd is still the best cell type for high-drain
> devices like modems and network adaptors.

Indeed, when you want to know the capacity of a battery, you need to
specify the discharge rate.

If you take a battery and draw 1A from it, and it lasts for 10 hours, you
could claim that it's a "10Ah" battery, 10 amp-hours.

If you tried to drain it at 10A, in theory it should last for 1
hour. But it probably won't. It might only last for 40 minutes. (that's a
random uneducated guess)

Battery capacity isn't really a figure as much as a graph.

Basically, msot batteries get worse the more power you draw. How much
worse they are depends on the chemicals inside, and the shape of the
elctrodes.

gopi.

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