ORIGINAL: DustBen
ORIGINAL: jimmyjames213
Instead of guessing how long a battery will last and how much the servos draw, just test it?????? Sit on the couch and move your ailerons and elevator while watching TV. Start the clock when you first start moving the sticks; stop the clock when the battery dies. When your battery finally dies, divide that by your flight time, and that’s how many flights you can fly on that battery. There is already a huge % error built into this method, the fact that your control surfaces are moving nonstop, what this means is if your flight time is 10 min and your battery lasts an hour you can safely get six flights in. Realistically that battery would be fine for 12 flights due because I doubt a trainer is constantly doing rolling circles, but cut it in half to be safe and you should be good to go.
electricity can be hard to understand and trust for some, the easiest way to understand it is to see it in practice. Instead of guessing just test it, if your battery lasts an hour of constant elevator/aileron servo opperation (just move the gimbals around the corners) and you know for a fact you are not doing that in the air, then you should have plenty of juice for 6 flights at 10 min per flight
I have to warn against the idea above.
The flight loads under speed exerted upon ailerons, elevators, and the rudder greatly increase the resistence to movement. Assuming battery consumption in flight is the same as static loadings is not accurate.
I fly some pretty light designs and have some relatively tiny flight batteries.
The way I determine the mAh size I need is to start with a robust battery around 750 mAh. I fly the model wildly... consuming about as much as I can.
As quickly as possible, I check the ''end of flight'' voltage (this is critical because a battery can rebound and if I check the voltage 30 minutes after flight, the voltage will read much higher than the actual, post-stress voltage).
I then carefully recharge the battery and observe the amount of mAh it took to restore full capacity.
Meanwhile, I begin downsizing the battery. I drop to 600 mAh and repeat the careful monitoring of mAh consumption and voltage.
Once I determine a specific ''consumption'', I get a battery of slightly larger mAh capacity and begin using it. I fly shorter flights at first, always checking the health of the battery at the end of the flight.
While I understand every bit of being conservative with flight packs, I also hate putting a 6.7 ounce battey into a 2-3/4 pound model when I can safely get by with a 40 gram 350 mAh pack.