jb92563 wrote:
I use one of these:
http://www.harborfreight.com/cpi/cta...emnumber=44768

View the product manual for details.

At 1.5 watt it keeps a small motorcycle battery charged indefinately
for powing a typical instrument panel with radio and audio varios etc.

a 5 watt panel might be too much and will need a good charge reulater
so as not to cook the battery.

You need to measure your current drain before getting too excited about
solar panels. A PDA can draw 300-400 ma; for a 5 hour flight, that's 1.5
to 2 amphours. A 5 watt panel can put out, at most, about 300 ma with
perfect alignment to the sun. On a glider in flight, it will likely
supply an average of maybe 100 ma. Do the math.

Sitting on the ground, it will still not be perfectly aligned with the
sun, so even when you count the amps over a full day, it might not keep
up with the PDA, and you still have a radio, vario, gps, maybe more.

Result: 1.5 watt is quite inadequate for the typical glider, and you
need solar panels that can put out at least twice the normal current
drain to just keep up. Of course, if you fly only 2 or 3 hours a day,
you can get by with smaller panels.

The reason pilots are willing to pay the big bucks for the Strobl solar
panels is they put out a lot of current for their size, so they can
actually keep up with the typical radio, vario, gps, PDA, and (with four
panels) a transponder.

An alternative is to charge your glider battery from another 12 volt
panel, using a Multiplex Ln-5014 DC-DC charger (or similar). Much
cheaper, and you don't need to install solar panels on the glider. The
DC charger battery can be charged by an AC charger or small solar panels
during the day.

--
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