ESC shutdown problem

I’m at the first flight stage with a scratch-built quad using an APM 2.5 but I’m having problems with ESCs cutting out. I have my friend arm the quad in Stabilize while it’s on the ground, then I pick it up and hold it firmly, then my friend throttles up to low throttle. Each motor seems to respond correctly – when I rotate the motor downward, it throttles up; when I rotate the motor upward it throttles down (authomatically). But, when I request a larger amount of power (for instance, if I aggressively rotate two motors down at once), all but one of the ESCs seem to just shut off (the motors stop spinning). If I put the quad back on the ground, disarm, then rearm it, all the ESCs are fine again.

It seems like this is likely a low voltage issue where my power system can’t deliver enough power, so the voltage droops, so the ESCs’ microcontrollers shut off one by one. When I stop requesting power, the voltage comes back up, but the ESCs don’t immediately rearm because the servo signals aren’t all the way low. When the quad is disarmed, all the servo signals go low and the rebooted ESCs become active again. When I rearm, all the ESCs are ready to go again and the process repeats.

This makes sense as an explanation, but I’m not sure it’s right. I have smallish motors that I expected to take around 10 Amps each (I can look up exact specs if that’s critical), and less in easy test flights. I have 30 A Redbrick ESCs because I wanted them to have plenty of headway so I wouldn’t have to worry about thermal issues. The quad weighs 1.17 kg with the small test battery, all ready to fly. My test battery is a 20 C 2150 mAh Rhino, so I expected it would be able to put out 40 Amps for the test. I have a larger flight battery, but haven’t yet attached a connector. My power distribution is a ~3" length of flexible 12 awg wire that leads to ~7" of solid 12 awg per channel with 4mm bullet plugs to the ESCs, and then 3.5mm bullet plugs to the motor.

It seems as if the battery being too small is the most likely issue. But, I wouldn’t have expected it to be too small for non-aggressive test flights. Does this seem likely, or have other people experienced similar problems?


I guess this is quite an old post but in any case, I strongly suspect you’re right that it’s the small battery that’s causing the problem. If you are using a 3dr power module you could see how much the battery voltage is sagging as you throttle up. … -with-apm/

 This information would appear both in the dataflash log's CURR message and in the mission planner's flight data screen's status tab (bottom left).