For those who have the same 8FUN/Bafang centre motor as on my bike, the C965 motor controller display shows the reserve for an instantaneous call of current on the battery, somewhat like the current Rolls-Royce which scorns a common tachometer in favour of a power reserve meter.
It is the bar graph below the halfway mark on the C965.
On the flat under all normal conditions of operation it will show all bars but on a steep hill it might progressively show fewer bars, and that is the current available for instantaneous power demands.
We'll refer to it as a Coulomb Gauge, the coulomb being a charge of one ampere for one second, so C = A x s, the very notation telling you it is a short term measurement, which is why I called it "instantaneous power" i.e. a level of power so high that if you used it for many seconds and often, it will definitely reduce the lifespan of your battery.
The larger your battery is, the less likely you are to see less than the complete bar display for more than a few seconds at a time. That is why I advise those fitting an electric motor to buy the largest battery the budget allows. A larger battery has, to simplify the matter to Jeremy "The Hammer" Clarkson's level, the guy who talks about "torques", more coulombs.
Mo' coulombs is bettah coulombs!
