There are already good and proven monitors out here with the hassle of building one yourselfEagle Tree Systems
Hello, I'm looking for advice on how to monitor the battery levels of a quad-copter.
That is what the OP is proposing. Coulumb counter.100 Amps for 1 second is the same charge as 10 Amps for 10 seconds assuming constant voltage.With a quadcopter both situations are feasible.However both conditions have a different effect on remaining charge.100 Amps for 1 second is also very likely to reduce terminal voltage.The charge monitor has to take this in to account.Testing and calibration is needed for the battery, this is probably done for the likes of cellphones and the eagle tree unit but is probably a bit tedious for a one off.
I have tried this using a telemetry module but abandoned it in favour of using a timer as the information did not prove useful in practice.It may be useful for something like a photography drone though. EDITOr anything else where the drain is relatively constant.
I see your point. But how'd you use a timer to monitor your battery levels?
Something that could work is to monitor battery voltage when in low power operation and indicate when 40% capacity is left by audible, led or telemetry.Then you stop doing hi G manoeuvres which could cause brownout , 40 % being enough to retrieve your model.For the likes of fixed wing or photo drones probably 30% is enough margin.
Good idea, I'll be sure to include that feature.Here's a good log I found.
Check sparkfun.com, they have several "fuel gage" chips on breakout boards for monitoring LiPo charging and discharging, etc.
The popular batteries have proper documentation of their voltage changes depending on their battery level.