[Canberrauav] GEB Battery testing results

Andrew Tridgell andrew at tridgell.net
Wed Feb 4 17:51:00 EST 2015


Hi Chris,

Thanks for chiming in!

> We have a ultra capacity battery line coming out soon based on the GEB
> cells, from speaking with the factory and our test found these batteries
> have a lower cutoff voltage than standard LiPo's and using the new spec can
> achieve spec capacity at 1.5c We geared the line for HV multi rotor setup
> 8~10s that pull minimal amps, well with in the batterys C rating. What
> voltage are you terminating your test?

As James said we terminated at 12.5V loaded voltage on a 4S 12Ah pack
(2x4S 6Ah in parallel). The load at 12.5V was around 19A. So that is
3.13V per cell at around 1.5C load.

The unloaded voltage at that level of charge was about 14.7V (around
3.7V/cell).

What loaded cutoff voltage would you recommend for these cells to give
us about 10 to 15% remaining capacity to bring the plane home?

The other issue we noticed is that because the voltage drops so much the
usual Ah rules of thumb get pretty bad, as the current draw to keep the
plane in the air kept rising. So you really need to talk about Wh not
Ah, and the usual autopilot failsafe code based on Ah consumed is
perhaps not the best approach. Have you thought about that at all?

Ideally we'd have an equation modelling the behaviour of the battery
under different loads, so we can properly calculate the amount of
capacity remaining for failsafe handling.

Cheers, Tridge


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