The system power is comprised of different elements.
Battery Power
From the battery it is: Voltage * Amps = Watts
Example: 52V *57A = 3000W
72V * 41A = 3000W
Voltage being your batteries nominal voltage.
Amps being your max amp output of your battery.
Wattage is combined voltage * amp
Motor Power
Motor power is distinct from battery power, in which as you use your throttle to command more torque and speed. Current is pulled from the battery and then into the controller (also known as the inverter) which then amplifies or inverts that current and multiplies that current which is then fed into the motor. This is called phase amps.
Phase Amps
Phase amps is current going into the motor, which can be much higher than battery current especially when accelerating from a stop to mid speed.
We can see by analysing this chart the relationship between battery current, battery voltage, and motor current.
As the vehicle begins acceleration from a stop, motor current will ramp quickly (yellow line) and remain at peak until mid speed.
Battery current (red line) ramps much slower than motor current and does not peak until mid speed.
Battery voltage (green line) falls as more current is pulled from the battery, this is normal (voltage sag).
In general, phase amps will determine your acceleration power from a stop to mid speed, and battery amps is responsible for mid speed to top speed performance.
Note that, in the chart there is a 3000W system imposed limit. Otherwise battery amps will continue to rise, and due to field weakening, battery current will continue to be pulled from the battery in order to achieve a higher top speed.
System Power Configuration
To set your max system power, you must configure these parameters.
Rated motor power = Set this to the max power that your battery and motor will allow. This will be Battery Voltage * Battery Current = Wattage. Example: 72V * 118A = 8500W
Battery Current Limit % = If this is set to 100% then the controller will allow 100% battery current to match Rated Motor Power.
Example: if rated motor power is 8500W, then setting battery current % to 100% will allow 118A current in order to meet the target 8500W rated motor power.
If rated motor power is 8500W, and battery current % is set to 50% then only 50% current will be avaliable, and peak power will be cut in half, which is 4250W.
You can set battery current % higher than 100%. Example; rated motor power is 8500W and battery current limit % is set to 200% then battery current limit will double at 236A ( 72v * 118A * 2). Your peak power then will be 17000W @ 72V 236A.
Basically Rated Motor Power together with Battery Current Limit % will define the max battery power limit, be careful not to exceed the capabilities of your battery and bms, as this could be potential dangerous.
Rated Motor Current = This parameter defines your maximum phase amps. Example; setting 100A, the controller will attempt to set 100A as the target peak motor current. There is always a chance that the controller might overshoot the target phase current value (which can be reduced by adjusting the current regulator). Also setting a high rated motor current number does not necessarily mean the motor will achieve that number.
This is because there is a correlation between Motor current and Battery current, this is known as the Phase amp to Battery amp ratio, it is shown in the chart above. Thus a limitation in battery amps will also limit peak phase amps.
Be very careful not to exceed your motor's capabilities, as this might burn out your motor.
Calculated Battery current Limit
Adding these parameters will allow the controller to automatically calculate your max current limits based on your settings.