"Willy VINKEN" wrote in message ...
On 5 May 2004 09:08:46 GMT, Brian Penfold
wrote:

Capacity is measured in Amperes per Hour (AH) ...

Brian,

I think this should be corrected:
'AH' actually stands for 'A x H' and means 'Amperes times Hours'.
'Amperes per Hour' would rather be 'A/H'.
Or do I miss something?

Besides this, I agree with your point of view.
Adding a 2v element to a 12v battery could make some
sense to increase the RF output of the radio, since a
transmitter power amplifier output transistor usually is fed
directly from the battery, not via a voltage regulator.

With the radios you and I fly around with, they're always fed
directly from the battery. Claims that they use regulators are
bogus, made by people who are too cheap and lazy to put together
a proper battery for their radio, and want to rationalize why a
12 volt battery on a 14 volt radio is such a great idea. Strangely,
no one ever just says, "Hey, I'm just too cheap and lazy". In one
of these discussions, someone even claimed that most radios have
switching regulators built in. It's amazing how people can convince
themselves of whatever they want to believe, if they think they can
save a buck.



On the other hand, a freshly loaded 14v-nominal battery
probably exceedes the allowable voltage of most of our
electronic equipment. It's not worth the risk.

Not at all. The standard for small aircraft has been taken as 13.8
volts for about 75 years now. In reality, alternators and generators
provide 14-14.5 volts to keep a 12 volt battery fully charged. That's
why your radio will have a max voltage spec on it of 16 or 16.5 volts,
to provide some safety margin. If anybody starts selling avionics that
blow up at lower voltages, people should boycott them. It would be
*really* stupid to do so.


Willy M.D., -not- engineer... ;-)


Dave (who is an engineer, but who knows the difference between ampere-hours
and amperes/hour)