How is "Percent Remaining" calculated?

ArduCopter Copter 4.5
1

I’m working on finding proper failsafe voltages for a copter with a 4S 5000mAh Lion pack.

I try to set my failsafe to trigger at 80% usage. In this case - with about 4000mAh remaining.

The voltage I’m using seems to work out OK - but the “Percent Remaining” statistic in the log and on the ground control telemetry shows 40% remaining. It should say something closer to 20% remaining.

Is there anything I can to to adjust this?

BTW - I’m using resting voltage for my failsafe voltage level.

image
image1920×1080 91 KB

As reference - here’s the voltage plots:

image
image1920×1080 93.5 KB

Many Thanks!

2

It’s not based on voltage, it’s current consumption.

3

That’s what I thought. But after using 4000mAh out of 5000mAH it should report 20%, not 40%.

Am I missing something?

4

Double check that BATT_CAPACITY is correct.

5

I am not sure but I assume the FC is calculating on the measured current and integrat it over the time. This is the normal way to do it. But it needs a good calibrated current sensor.
The voltage is not a good indicator for the used power as the discharge curve of LiIon is over long time relative flat but at the end it is changing very steep. Also the voltage drops with the load of the system.

1 Like
6

Yes sir - I somehow had the old BATT_CAPACITY value of 6500.

Thank you. I feel kinda dumb now…

1 Like