Which sustainer system would you chose for your sailplane?

On Sunday, September 23, 2012 10:16:30 AM UTC-7, John Cochrane wrote:



From an engineering standpoint, I don't really see why the electrics

don't also charge the battery. If you climb to 3000', in 20 minutes,

surely running the prop in generator mode for 20 minutes or so,

doubling your sink rate temporarily, should recharge the batteries?

This could make a 3000' capacity enough for self launch and

retrieve!.



John Cochrane

John,

I'm not an engineer by any stretch, but your question seems to presume 100% effeciency. Even under ideal circumstances propellers are closer to 80% - - so that would be at least a 20% loss on both discharge and charge.

Then there's the heat loss due to friction and resistance of leads and internal motor windings. Couple that with battery heat generation and loss due to internal resistance and chemical processes on both charge and discharge. All this may have one pointing downhill charging batteries for longer than might be comfortable. I get uncomfortable just thinking about it (g).

bumper
ASH26E . . . like those old Mazda commercials, Wankel engine go MMMMMMMMMMMMM!