I am using also 2 batteries. Both are 7 amps but li-ion. Strong enough for my
engine. One is to start the engine with awg 8 and one as a backup for the fuel
pump and ignition with awg 12. One batterie gives me 20 min. So if I have a alt
failure I have at least 40 min flight time left.
Both batties are 1.6 kg including fire box and mount each. If you are
> Op 11 augustus 2018 om 0:48 schreef Mark Langford via KRnet
> Paul Visk wrote:
> >> Mark L., I noticed on your wiring schematic on your website you
> have a 7 Ahr backup battery. Would you still recommend that size? Is
> it large enough to turn the engine over while airborne?I'm at a point
> now to where I can pretty much put everything on and do a
> weight-n-balance and find out if I need to move my corvair engine
> forward to pinpoint my cg.<<
> I never intended or expected that little 7Ah battery to start the
> engine. It's there mainly as a backup power supply for fuel pump and
> ignition system if the rest of the electrical system goes up in smoke.
> It's isolated by a diode to keep it from being compromised by a main bus
> melt-down. I do test it by starting the engine on it, which also takes
> some electrical load off the main battery while it's spinning the engine
> over using the main battery.
> As a data point, my experience has been that a high compression Corvair
> with a 54" prop will not restart in a glide if there is no power applied
> to the starter, not even if you point it at the ground and run it up to
> Vne. The starter circuit won't be the thing that makes your engine
> quit, and it's so simple it's difficult to see how it could fail in
> flight unless as a victim of collateral damage. Running out of battery
> "juice" due to an alternator failure and not noticing the voltage drop
> is probably when you'll find a backup battery the most useful. When you
> do notice, you should have some idea of how far you can fly before you
> kill the backup battery....to avoid unpleasant surprises. You'd
> probably want to head for nearest airport with something like a 7Ah
> battery. Your Corvair ignition system probably burns 3A at 3000 RPM,
> with another amp going to the fuel pump, but that doesn't mean you can
> fly almost 2 hours if you are running purely on the 7Ah battery.
> For those who haven't seen it, the electrical system Paul is asking
> about is at http://www.n56ml.com/electrical/index.html .
> Mark Langford
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