I have just taken my newly built 3DR Arducopter (APM) out for her maiden flight. Essentially she seems underpowered.
At first she would lift ok and then slowly drop to the ground. Then after a minute or so of repeating this, eventually the motors got slower and slower until they wouldn’t even spin at max throttle.
At first I obviously though that the battery had discharged, until I plugged it in to the charger to see that it was actually at over 9v.
Does anyone have any ideas please?
Actually I just read another post and for a 3s lipo this is probably as discharged as it should get?
It does sound like your battery is running flat. Are you using a 3S Lipo 
In terms of a 3S lipo battery the voltage should be about 12.2V when fully charged, and should not really go below 9.6V if you want it to last, usually ESC’s would stop when the voltage drops below 3V, but this feature is usually disabled with mutirotor ESC’s as you don’t want a motor to suddenly turn off when you are flying!
Could you also give me some more details of your quadcopter in terms of the total weight, and what motors and props you are using as it could also be too heavy or under-powered?
Luke, please tell me what you did to solve this problem. I’m building a Hexacopter with a Pixhawk and getting Thrust Fail with the same behavior you wrote about.
It does sound as if your battery is either damaged or just low on power, what voltage is being reported on you batteries from mission planner, and what would be better is to measure the battery voltage directly and see what it is, as if you are using a 3S battery it should not be much below 9.6V.
Thanks. I’m using multiple batteries. Just today I had two different batteries go into Land from Battery Fail Safe. Both of them still had 11.7 when I checked them using a battery monitor. I wish I could find out why my voltage is dropping.
Here are two suggestions that you could try.
Check your setting in mission planner to make sure your failsafe has been set correctly as you can set it to enter battery failsafe based on voltage, or voltage and capacity, also make sure that the battery voltage and capacity are set correctly on your autopilot via mission planner, as sometimes the power module could be out slightly. If you need help on how to calibrate your power module just let me know.
If the first step did not work then the next thign would be to connect a watt meter to your system and run your copter (with the props mounted to push downwards, or your copter tehteered securely down to the ground ) and monitor what the voltage, and current draw are to make sure everything is functioning as it should. As it could be an issue of your motors pullling more current that the battery can handle (what is the C rating and capcity of your batteries btw)?
Hope that helps
I haven’t solved the problem and now my quad is collecting dust!
I have just replied to your older post here with some more things to try/check.
However within mission planner is it now reporting the correct voltage, and have you set the battery failsafe correct?
