AVR-Chat

On Fri, Jan 23, 2004 at 07:45:28PM -0500, Dave VanHorn wrote:

> While we're sort of on this subject, let me relay a little
> research into memory effect on NIMH.

> http://www.dvanhorn.org/NIMH/Index.php

> It's about halfway down the page.

Interesting.

One of the problems with maintaining rechargeables is the "memory"
effect that's certainly evident in NiCd.

If one isn't stuck for space and weight isn't a problem, then it may
be appropriate to run two battery packs in tandem; one which is the
backup supply and the other being cycled so as to avoid the memory
effect. 

Full redundancy requires 3 battery packs as the power supply
requirements to charge a NiCd to make it forgetful is quite high.
There'd be "backup", "source" and "cycle" packs.
The source battery pack is used for the initial current supply while
the voltage of the cycle pack being charged is low. The boost
current from the source battery depletes a large part of it's charge
so a backup pack is required for "fail-safe".

With just 2 cells, the backup and source batteries are the same.

The condition of the batteries can be monitored and notification
(light/audio/signal) of a failing one made by the controller.

It's a pretty obvious approach if you're looking for improved
reliability of varying degrees. Cost is an issue that must be
weighed against the benefit of increased reliability.

-- 
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