zoomkat:
One thing that can happen is it burns out. With inadequate supply the circuit
may malfunction and pass full supply through the servo's motor, until it overheats
and gets damaged.I doubt that the motor will be damage due to low voltage. I've never heard of RC hobby servos being damaged by trying to power them from somewhat discharged batteries.
True but I think MarkT was thinking under a premise of some near-impossible circumstances, that -could- damage a servo, under a -very- specific circuit.
At first this didn't make sense at all: 'With inadequate supply the circuit...' 'pass full supply through the servo,' because inadequate supply -implies- 'less than full supply,' and is therefore non-possible.
The one case where it's possible is if a circuit is controlling the servo voltage level, and that circuit is powered from a different source than the circuit power source, and goes wonky when the -circuit- voltage level drops, while the -servo- power source is still -capable- of delivering a higher voltage. But that's got to be a rare-rare design. (Mmmm maybe not extremely rare, but Occam's razor says to think as 'simply' as possible unless advised otherwise.)
What I believe OP -meant- in -typical- design is that servos and control circuit are powered by the same source. Or I have to at least -assume- that because he didn't state anything different (again Occam's razor.) With that it depends on how the controller behaves when voltage is lowered. Yes, servos may go to wonkland, because controller has also gone there -first-. But other than that, no, simply low voltage can't 'hurt' a servo.
Bottom line though is that any assembly (especially with a non-simple power source design) that has -potential- to hurt either itself or people around it should have some sort of voltage sense circuit, plus a signal to the controller circuit, plus constant monitoring of that signal, so it can shut everything down safely if voltage drops below a certain level.