I noticed that on Amazon they sell a spare 36V battery which is rated for a current draw of 10 amps maximum... but the motors are rated for an output of 2x250 W, so their combined maximum output would be 500 W, which makes them draw even more from the battery... but the battery is only rated at 360 W maximum output! Granted, this is only the peak output... if you're only rolling on the flat, you will maybe use 100 or 130 watts, but when climbing hills, you may exceed the maximum rated output of the battery for a longer time.