I have a simple question about electric flight: where is the fuse (or fuse-equivalent)?
Long, long ago I learned that the purpose of a fuse (the thing that melts when too much current goes through it, not slang for "fuselage") was to protect the wiring in a circuit, not the device at the end of the wire. That makes sense.
Now let's look at a typical setup:
Bat --- ESC --- Motor where of course there's another branch, too:
ESC --- Receiver --- Servos
Suppose that something goes wrong at the motor -- your anti-noise capacitor gets shorted, for instance. Suddenly you've got a large potential current draw at the motor, and it seems like a good chance to melt the motor wires, the Bat ESC wires, or both. If the ESC has some sort of over-current protection, you're probably OK...but if not, you're headed for a fire.
This isn't entirely hypothetical, of course -- while flying with my kids, with a 700mAh Lipo powering a J250 motor, this is just what happened to me. The time between "hunh...something's wrong here... the prop isn't turning when we goose the throttle" to "there's a smell of melting/burning insulation" was about 6 or 7 seconds, tops. By the time I grabbed things and ripped them apart, I had a couple of pieces of burning insulation and an ESC that looked like a small roman candle. (Ammazingly enough, the plane -- fanfold foam -- was undamaged. Damn. Why couldn't the $.50 plane get wrecked and the $15 ESC be saved?)
So...should I henceforth solder in a fuse in the battery-to-ESC wire? Something like 7A fast-blow should do the job, since that's the top discharge rate for my 10C lipo, right? At the cost of a few grams, I'll feel a lot safer...
--John