Design thinking behind Arduplane BATT_WATT_MAX

ArduPlane
1

Hi guys

I tried using using the BATT_WATT_MAX parameter to limit the power output of my plane, especially when it’s initially on a full battery and performing a climb. The Motor is limited to 400W power due to packaging, while at high voltage at ESC’s rated current, the motor will blow.

So I ran a quick ground test where I set the BATT_WATT_MAX to something very low, 200W, tricked the airplane into flying in auto, and I would see the throttle reset to 1300PWM as soon as the power threshold is triggered. It will slowly creep up to the threshold again, before dropping to 1300PWM and repeating the creep back up. I looked into the code and it seems to be working the way it’s designed to.

My question is, why was it designed this way? why can’t we have the throttle bounce off the power limit or sustain the power limit? why is it designed to significantly drop the throttle and ramp back up slowly?

PS. if you fly the plane in manual, it will throttle back to 1300 and stay there, making it very difficult to fly.

2

The battery voltage changes, so the limit must be tested dynamicaly. Please set it 400W and you will be fine.

3

Well I cna’t really do that. Say if I’m flying close to stall, and I need to speed up, all of sudden the power limited cuts throttle to 1300pwm, i’m going to crash. I get it that it has to be tested dynamically, but why drop it to 1300? It’s not like the battery voltage collapses that quickly. That’s the logic design I’m trying to understand.

4

1300 pwm is due to the 200W limit. 400W will limit it at another operation point. Can you provide .bin logs of your flights