On Feb 5, 7:43*am, rk wrote:
On 3 helmi, 18:10, JohnDeRosa wrote:

At the panel I use three switches to run the batteries in parallel.
Battery 1 on/off, battery 2 on/off and then the output of both to a
master switch and then to the avionics. *The thinking of separate
battery switches is that you can disconnect a "bad" battery. *I always
have all three switches turned on during flight - the need to be able
to turn off a bad battery hasn't arisen for me and I am unsure how I
would even know (everything dies? *smoke?).

You would know that by total power loss of all your batteries. You
have essentially parallel connection with all your batteries during
flight. When one fails, it drains your good batteries empty. When your
radio or computer starts blinking it's too late. Best option is to use
simple selector switch to choose one battery at time, and keep other
batteries disconnected.

rk

I've been using a somewhat different approach. Two batteries, each
powering half the avionics. So batt 1 has the radio and nav computer
bus; batt 2 has the logger/PDA and backup vario bus. Instrument
"busses" hooked up via individual 3 position switches so that either
buss can be powered by either battery or disconnected. Normally, run
the batts/busses independent, but have had occasions when one batt
went low early, and just switched the bus it was on to the other
battery for all instruments for rest of flight.

I also use the built-in voltmeters in various instruments (AR-4201,
SN10) to monitor the health of the batteries during flight.

Seems to work OK for the past 12 years...

Kirk
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