Okami said:
Maybe temperature also impacts why Ah and WH numbers are off from each other, when I calculate WH count from consumed Ah times voltage.
you can only really "calculate" wh from ah (and voltage) if both amps and volts stayed constant during the charge or discharge. if either changes, then the calculation is at best an estimate, and if they constantly change, like on a ride, it is a rough estimate.
if you were just doing a normal charge, or benchtest discharge with a fixed load, then because the voltage and current curves are close to opposite, a calculation is likely close enough.
but if you were riding around with the load constantly changing, so current increases and decreases constantly and by essentially the full range of allowable system currents from zero to max, and the voltage both sags during higher currents, and drops as battery discharges, it isn't necessarily going to be a very good calculation. if you based it on the average current, assuming zero as minimum, and max current detected as maximum, and average voltage, assuming full charge voltage as maximum, and the lowest voltage sag detected as minimum, it is not likely to come out the same as a fully-measured wh tracking would--it might be significantly different (probably would be).
it may still be close enough for range estimations, pack health tracking, etc., but if you want accuracy...you'll have to measure everything as you go.
Though it doesnt really change wattage needed, its demand, so even if volts are lower, amps would be higher to compensate.
that isn't necessarily true. it depends on the electrical situation.
for instance:
in the phase wires, this is nearly guaranteed to be true, because the resistance of the motor itself is so low.
in the controller-to-battery wires, it will depend on the situation, load, and controller design / software (and settings, if any).
if, as is common for generic cheap ebike controllers, the controller is not setup for monitoring and controlling power draw, or motor phase current, but rather battery current, it is going to attempt to keep battery current constant, regardless of battery voltage, assuming a specific load on the motor. (especially one that is at the max battery current allowed by the controller). especially if it's a common "pwm" or "speed" throttle, rather than a "torque" or "current" throttle, or the less common "power" throttle.
that means that the measurements, taken on the battery/controller wires, won't get higher currents as voltage lowers, because the loading doesn't stay teh same, as the controller is not attempting to keep the motor outputting the same power. instead, the battery current is kept the same, so total power in the system drops as the battery discharges and decreases voltage. moreso as the battery sags in voltage more for the same current load as it gets closer to empty.
if you're never anywhere near the max battery current limit of the controller, then you will see current increase as voltage drops in various situations, assuming the load on the motor stays the same to cause it to draw the same amount of power...but this doesn't typically happen on a whole ride, or even more than short stretches of one.
if you have a controller that measures phase currents, and is controlled by a "current" or "torque" or "power" throttle, it is going to be trying to keep the *motor* current constant for a given throttle setting, then it is going to be trying to keep the loading constant, and that *will* increase the current as voltage drops, up until you've maxed out the current limit of the controller (if it monitors battery current in addition to phase currents--if not, it may not actually stop increasing the battery current draw, so there wont' be an artificial plateau).
