Sealed Lead-Acid batteries Do Not like to be run dead. Ideally, they never should drop below 50% of capacity before being recharged.

Now, we get into hype and sales pitches. The "Advertised" range of these little go-buggies is how far they will go downhill, with a tailwind, carrying a 30 pound load after a full charge on a cool day. The actual safe range is about 1/2 of that, 2/3 once in a great while. Otherwise, the battery sulfates - and dies.

Fuses are not voltage-dependent devices, but current dependent. So, as the battery starts to drop, and the regulator pulls more and more current (at a lower voltage) to the motors, the motors will start to overheat. And eventually the fuse(s) will blow to prevent damage to the motors.

http://batteryuniversity.com/learn/a..._to_prevent_it

Peter Wieck
Melrose Park, PA