On 15/12/2010 13:17, Olin Lathrop wrote:
> V G wrote:
>> 1. I have selected a power diode to drop the voltage of the initial
>> 5.8 volts to something less than 5.5 volts.
> I guess I missed something in the flurry of messages, but I thought you w=
ere
> now using a switcher so the input voltage above 5.5V is not a problem, in
> fact desirable.  Certainly a switcher can be set to deliver pretty close =
to
> 5V out, so what's 5.5V got to do with anything now?
>

Agreed. In fact you can use 6 x NiMH which is nice.

1) The Switcher is always dropping volts to 5V.
2) Voltage is about 10.2V down to 5.8V (or what ever you set lower safe=20
limit at between 0.9V and 1.0V per cell. Consult data sheets and allow=20
for component tolerance)
3) Not too many cells so easy to turn off to avoid reverse charge
4) with 6 x AA you have about 50% more capacity than 4 x AA
5) Battery discharge starts at about 590mA for 1A 5V out assuming only=20
85% overall efficiency.
6) Easily charged from Car socket using linear series current source=20
with less dissipation than a 4 x AA pack. (Assume 14.2V average voltage=20
when engine running)
7) There are holders for 6 x AA, common in two styles.

WARNING
many battery holders for AA are not suitable for prolonged use at higher=20
current. One model the steel, chromed springs get hot and melt the=20
plastic case and rivet can be pushed out by spring on negative and short=20
to metal case :-(



--=20
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