I've got an Arduino Nano hooked up to 4 brushed DC motors in an attempt to build a micro quadcopter. The whole thing is powered by a 3.7V LiPo battery (240mah, 20C, 1S). Since the battery only provides 3.7V I also have a DC step up board that provides 5V to the Nano.
When I plug the battery in and having uploaded a sketch to run the motors at 50% speed, the whole system runs for about 5-10s and then stops. During that time the motors are decreasing speed. Once the motors stop completely there is no power anywhere on the system. In fact the battery is no longer providing any power! Initially I thought that the battery had lost its charge but hooking it up to a charger for 1-2s is enough to repeat the whole process.
Hooking up the battery directly to a motor works fine and the motor runs at full speed. The battery comes with a protective circuit and I'm suspecting that something 'trips' on that circuits and cuts off power. Hooking it up to a charger 'resets' it and it starts providing power again. I've read in a couple of places that LiPo batteries with protection circuits can go into a 'protection' mode, but I think I understood that to mean to protect from undercharging (which is not what's happening in my case).
My next thought is that I'm perhaps drawing too much current....which I'm finding hard to believe though. I measured the pull from a single motor to be 65-70mA. So 4 of them would be 280mA plus whatever the Nano, the DC step up and the other components (gyro, RF24) draw. The problem is that when I hook up my multimeter between the battery and the copter it measures 45mA but the system doesn't quite run! it sort of kicks off a little then dies, then kicks off again, each time the motors spinning for like 1 degree. Take the multimeter out and it's back to the original behaviour (run for 5-10s then die).
Any ideas what's going on? Or something else to test?