Bill Daniels wrote:

I don't think it's fair to say that Li-ion in some form wouldn't work as a
starter battery. It is fair to say we don't yet know all the issues
involved.

I agree. I was addressing John's situation. I'm sure a competent battery
engineer could design a good starter battery, though the voltages
available in Li-ion might be challenge for a 12 volt starter.

snip


As for temperature and altitude, I just can't see that as a problem. The
pressure delta from sea level to 40,000 feet is something like 10 PSI. The
cases have to be much stronger than that for safety reasons. Low
temperatures might cause a battery not in use to not develop full power at
switch-on but one in use would maintain its own temperature.

I suspect these batteries are probably fine for our conditions. The
problem (for me) is I don't know what's in the external laptop
batteries. Are all the components capable of 40,000'? If the pilot takes
off at 105 deg F with a battery at 130 deg F under the instrument
cowling and climbs to 20,000' in an hour, is the battery still OK, or is
it overheating under the load from the Ipaq, transponder, glide
computer, radio, etc.? Or maybe he just struggles around a few thousand
feet off the ground, while the battery temperature goes up? What then?

Sure, for pilots flying in temperatures under 90 deg F and less than
10,000', I'm not worried about the ambient conditions, but that leaves
out a lot of pilots in a lot of places.
--
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Eric Greenwell
Washington State
USA