Cell mismatch at high current
I discovered something that should have been
obvious, but I never saw it written anywhere.
When drawing high current from a Lipo,
like 25C from a 30C battery, the mismatch
between cells is magnified, and can be
detrimental as the battery is depleted.
After a couple of short flights the battery's
three cells showed 3.80 to 3.83 volts, .
still enough for another short flight.
The next flight I got a bit wild with the
throttle. Once I landed two cells showed
3.70 volts and one cell showed 3.48 volts.
Still above minimum voltage OK?
To see what the issue was, I ran the motor
up to full throttle with the voltage tester
connected. As the speed increased
the one cell voltage dropped off faster
than the others, and went down to 2.56
volts.
So it appears that getting wild with the
throttle early in the flight might not be
so bad, since there is plenty of voltage,
but doing it later in the flight, even when
there seems to be plenty of volts, is a
bit more risky.
I'm not sure if this battery is toast yet.
It might go into the Cessna instead of
the Corsair from now on.
Jenny