Hi John,

I enjoyed your article and just completed 2 test runs using the rig you detailed..I was mildly surprised to find 2 identical batteries with identical manufacture dates vary significantly on the results.

Battery #1 took 4:13 to run down to 11.5 volts, at about 5:45 it hit the "knee" at 10.5V described in the article and started dropping rapidly.

Battery #2 lasted almost an hour longer...5:10 to hit 11.5, then longer than 6:30 to get below 10.5V.

Both batteries were 12V 7.5 AH SLA.

Now I have a limited exposure to longer duration flights, heck I've not got my Silver duration yet, but I'm concluding from this test that, as long I stay off the XMIT button, I've got enough juice to keep electrons flowing as long as needed. My panel consists now of a Borgelt B-400 (soon to be Lx7) and an Oudie which I power off the ship. I've got a PowerFLARM brick on order and use a Lx Nano which I don't connect to the glider's electrical system. Hopefully, I have enough battery to power my expansion plans...your thoughts appreciated here.

A few questions? I've got an older Dittel radio (ship is an ASW 19b) that may be as old as the glider. The manual for the radio says it needs 13.5V to operate...obviously, it's getting nowhere near that. Last season, I had comm issues with other gliders or ATC facilities having trouble hearing my transmissions. Receive works fine for me. I was going to put the ship in a radio shop to test the transceiver, but now this whole electrical discussion has me wondering if the older radio is just needing more juice than a 12V battery can provide? Especially as I get 2, 3, 4 hours into a flight. Could that be a cause of the transmission difficulties? If so, do the newer radios work better on lower voltages?

Also, any anecdotal experience with battery manufacturers? I have a couple of "generic" SLA batteries that I picked up cheap...but now after my testing am wondering if brands like "Powersonic" or others might push my curves further to the right till hitting 11.5V...does price=quality in the battery world?

As to wiring, I jerked all the hardware/auto supply junk out and did the Tefzel wire as you suggested. Every component is fused, including the batteries. I decided to put in an A/B battery switch and a separate Master. Switching between batteries has never been a problem for the Oudie...probably b/c of its internal battery.

The one electrical failure I've had so far was not hardware related but human...I had flung the drinking tube to my Camelback back over my shoulder to get it out of the way one flight...when I retrieved it, it took some
tugging to get it back. I figured it had hung up on the parachute harness or seat back...Actually, it had snagged on the wiring leading to TQD connector on the battery. Tugging it (unknown to me at the time) disco'ed the TQD and killed everything. At the time I was 45 miles from home and my mechanical vario was inop...it would not have been fun for a newbie to struggle back home with no vario! Fortunately, flipping the A/B over to "B" got me onto #2 and home to a happy ending! The lesson I learned on this was...now I put a couple of winds of electrical tape around each of the TQD connections after assembly before securing them behind the seatback. Murphy struck, glad I had a backup!

Thanks again for the article, good off season project info!

Regards,

Rob S.
ZAP