Master Switch

Thanks, JJ. I have always turned the master switch on first and off last
and used the individual switches on the radios and instruments. I guess
it's that switching thing midway through the flight.

A large capacitor would be one way to mitigate that but I'm thinking more of
a "make before break" setup using multiple switches, i.e., turn on the
second battery before turning off the first.

Or I could simply divide my equipment across two (or three) busses and then
rely on the load division to allow the batteries to last an entire flight.

"JJ Sinclair" wrote in message
...
On Wednesday, October 16, 2013 7:26:12 AM UTC-7, Dan Marotta wrote:
A while back I was looking at LiFePO4 batteries to solve my electrical

problems and I may still order them as my SLA batteries are getting old
and

hold less of a charge.



I did, however, get behind my panel last week and changed out my master

switch for one more substantial in current capability and have experienced
a

major improvement in function of my equipment. The switch that was

installed when I bought the glider was adequate for the CAI302 and the

MicroAir 760 but, after installing a Trig transponder, a Dell Steak and a

Zaon MRX, all operated from the same bus, the current capacity of the
master

switch was the limiting factor. After two flights with the new master

switch installed it would appear that the problem is solved.

Ilec is dead set against using a master switch. The SB-7 manual has 22
cautions on the electrical installation page and the first 5 cautions are
why it is a bad idea to use a master switch at all.

"MAIN SWITCHES in the electrical system can be a source of serious trouble,
in particular where there are radio sets connected to them. When turning on
the main switch with the radio on, heavy negative going pulses may be
generated on the bus line during the typical 1-ms-bouncing periods of the
main switch. They can destroy instruments, if not at once, then in the long
run. We have measured pulses of more than 10 amps".
Ilec goes on and on about what a bad idea a master switch is in a glider.
What is the Master Switch really for? To shut off everything in case of an
electrical problem.......can you say, smoke in the cockpit? If you do use a
master switch (I don't), remember to ALWAYS turn it on FIRST and off LAST to
insure these potential 10 amp pulses can't get in your delicate instruments.
Hope this helps,
JJ