Battery life when running a transponder

hretting wrote:
Operating a 12v with a 2v (both 8amp/hr or greater) piggybacked to
it , running a 302, PDA, borgelt 400, Becker radio, and an old Terra
transponder gives me about 6 hours before I hit 10.5 volts on the
"left-over" meter.

10.5 volts is "100% discharge" for a 12 volt battery; it would be 12.25
for a 14 volt system. Taking the 14 volt system to 10.5 volts puts the
battery into deep discharge and potentially much shorter life, while
getting very little extra amp hours from it. The shorter life of the
over-discharged battery would quickly remove this small benefit.

I then switch to battery #2 and enjoy the ride.
Starting with 14v gives me the life boost I need. If I "dedicate" a
battery to just the transponder, I guess in excess of 8 hours. Wrap in
foam pack and it should outlast your Oxygen. How's that for "battery
life".

Dedicating a battery to the high-drain Terra might give you more hours
than the current setup (the lower the current draw, the more amphours
you can get from a battery), extend the life (years) of your batteries,
and eliminate the need to switch batteries.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org