AVR-Chat

Dave -
The question of adding an extra cell to an NiMH stack is one that is
vexing me at the moment.  I hope that this battery discussion isn't
too much off-topic, I appreciate getting people's battery experience
dumped once in a while.  Also, it's on-topic because so many AVR
projects involve portability and battery efficiency.
For those of us living off-the-grid, NiMH is a new promising improvement
over the ancient lead-acid technology and the troublesome NiCad.
I am trying to develop a modular portable power system based on
a unit of 10 or 11 NiMH F cells to replace the common 10 NiCad or
6 lead acid.  Use of 11 NiMH cells would give about 12 V at the low end,
which would be an improvement, and would only be too high (>15V) when
charging.  However, charging may be done out of the load system, and
in any case, most 12V inverters, lights, etc now can handle 15-16 volts 
because the recommended lead-acid equalizing charge in now up to 15.5V 
(although it still doesn't help extend battery life).
I'll be using the lightweight 12V modules in series and parallel
configurations
to power electric scooters, in-the-field 120VAC power packs, etc, and as house
back-up.  They can be charged anywhere where there is a temporary excess
of power.  And of course, the smarts for their interconnectivity,
manintenance, etc
will come from AVR!

Ken




At 02:50 PM 7/30/2004 -0500, you wrote:
>At 02:17 PM 7/30/2004, Ken Holt wrote:
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>>4 NiMH batteries is a good starting point, but remember that you'll
>>only get 4.4 - 4.6V (series total) over most of the discharge curve.
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>Actually, they are dead, for this app, at 1V/Cell, so 4V.
>An additional cell wouldn't be a bad idea, if the head can take the max
voltage.
>If the charger is connected while the head is connected, that can be
1.6V/Cell, or 8V.
>If you D/C the head while charging (and you need to have than mechanism in
place anyway) then you only have to withstand about 1.3V/Cell or 6.5V.
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>Yahoo! Groups Links
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