It is unbelievable what crappy electrical installations you can find
in gliders.
In my 1997 ship, somebody installed a 25 wire printer cable as a power
and signalling backbone under the seatpan.
Nice to be able to disconnect the panel at the DB25 connector if
needed, but...

I had continuous problems with my voltage dropping off soon after
launch to something like 11 Volts and my Dittel FSG71M starting to
blink.
I also ran a Terra250 and GPSMAP195 continuously.
After the batteries tested good on capacity, I checked the wiring in
more detail.
My ship has 3 battery positions (front, main and tail)
They were clever enough to combine 3 strands of the printer cable for
the positive terminal of each battery position.
I could not believe my eyes when I found out that they were running
ALL ground (power and signalling) through a single strand of the 25
wire printer cable.
If I were religious, I would have thanked God that the whole thing did
not go up in fire in flight.

My first project was to install a new separate power and ground
backbone with 12AWG Tefzel.
After that my power supply has been rock steady and pushing the PTT
button has hardly any effect.

Last winter I have replaced all of the remainder of the printer cable
(signalling) with Tefzel.
In the mean time also power hogs like the Terra has been replaced by a
Trig and the GPSMAP195 by a Ipaq310.

Then there is the never ending saga about batteries.
There are 2 use modes that substantially shorten the life time/
capacity of a battery (holds for most battery chemistries, but
particularly Lead Acid)
- Deep discharge
- Over charge
Most common glider batteries (like the PowerSonic 7AH) are completely
empty at 10.5 Volts at usual glider current draw (~1-2 Amps).
See the PowerSonic spec sheet.
Discharging to 9 Volts (at 1-2 Amps) is just damaging the battery.
With a reasonable AC mains charger like a Battery Tender or similar
2/3 stage charger, over-charging should never be a problem.
However, unregulated solar panel charging is a shortcut to premature
end of life for the battery.

As always on this forum, there are a hundred different opinions and a
lot of yelling about who is right or wrong.
I try to speak only about my personal approach and leave decision
making to the reader.

My approach is KISS.
I have plenty of battery capacity on board.
I have a good fat power supply (and ground) backbone in star
configuration.
I switch all 3 batteries in parallel.
I have no need for elaborate wiring schemes for switching of batteries
or separate batteries for separate equipment like transponder
I don't deep-discharge batteries (below 12 Volts) to prolong life time
of the batteries.
I have no need for voltage converters to try to maintain 12 volts from
a battery that is already empty (and damage the battery by doing so).
I charge all batteries immediately after each flight. Each battery on
a separate Battery Tender.

The FSG71M, Trig, LNAV, Ipaq310, Etrex are running happily and I am
sure the PowerFlarm will soon join without any problem.
Works well for me, but if you want to follow a different approach,
that is fine too.

Hans Van Weersch