Phase current VS Battery current...

[Alan B]

Reading back through this thread one confusion is the PWM will be changed by the controller if any limiting is in effect.

So the throttle position may call for 100% PWM (full throttle), but if the controller decides that battery or motor current would exceed the limiting values it will reduce the PWM to implement the limit. So the situations where the speed or load is changing and any limits are in effect the PWM will be changing as well. The actual PWM will always be less than or equal to the throttle's requested value, the controller only reduces it.

This makes analyses more difficult as we don't generally have a readout of PWM.

 

[molten_Cu_1984]

The term battery current can refer to several different things:

Actual battery current - the current you will see in an ampermeter connected to the battery at a given moment when riding.
Rated peak battery current - the maximal current the manufacturer claims that will not instantly fry the hardware.
Rated continuous battery current - the maximal current the manufacturer claims that will not fry the hardware when applied for an extended period.
Battery current limit - the maximal current the controller is allowed to draw from the battery.

The same terms apply for phase current (simply replace "battery" with "motor").

The actual battery current and actual phase current are constantly changing according to riding conditions.
The relationship between actual battery current and actual phase current is not fixed, it is also constantly changing according to riding conditions.

A simplified explanation for the relationship is: Actual battery current = actual phase current X %PWM .

The PWM is effected by motor speed, throttle position and load on the motor.
When at low speeds/high loads/a lot of throttle, the phase current will be much higher than the battery current and when cruising at high speed they will be very close.
If either battery or phase currents exceeds the maximum set in the controller it will reduce current draw accordingly.

For example:

Suppose the controller is set to limit the phase current to to 50 Amps and the battery current to 25 Amps.

If you are running at 25% PWM and the motor is drawing 40 Amps, the actual battery current will be 40 X 25%=10 Amps. No limiting is in effect.
Then a you start climbing a hill. Still running at 25% PWM, the motor now needs to draw 60 Amps. The phase current will be limited 50 amps and the battery current will be 50 X 25% =12.5 Amps.
After the hill you ride at high speed, say %90 PWM. The motor needs 45 Amps which means that the controller will need to draw 45 X %90 = 40.5 Amps from the battery. Since it is limited to draw only 25 battery Amps, the actual phase current will be 28 Amps (25 X %90 = 28).

I hope this helps to clarify things.

Avner.

I agree just to confirm though 90% of the 25 max amps allowed at battery should only allow about 22.5amps based on 90%? I think it may have been a typo but I'm just trying to make sure I didn't misunderstand your answer Incase I'm missing something? Great explanation though Avner