Does using Johnn in CR's method draw more current from the battery for less acceleration by having a smaller ratio of battery to phase? Or is actual battery current draw related not only to the controller battery current limit but as well as the ratio set? I need a DC current meter...
John in CR's method:
Step 1:
-Set battery current limit to something modest (low power)
-Set phase current to the same value (1:1 ratio)
Step 2:
-Apply 100% throttle and see how the motor spins up in free air
-Ride to feel what take off and top speed feel / sound like
-Increase only phase current a small step
Repeat testing and increasing phase current until the motor sounds and feels to be powered properly.
Do not expect powerful acceleration yet.
Step 3:
Note the ratio you have reached and increase BOTH battery and phase currents while maintaining that ratio found in Step 2.
I have an 18 FET 4110 and it came from factory with a 65A battery limit, and a 2.8 Battery to Phase ratio. My motor is a "1500W" 10" Scooter motor with a kV of 16.5ish.
I was unable to notice any starved properties at 1:1 (60A, 60A) other than it barely produced any torque. Free air spin up seemed the same.
I reached a ratio of 1:1.5 battery to phase where I could actually move around. I decided at this point to use this ratio to up my battery and phase amps.
I am now at 88A battery with a battery to phase ratio 1:1.55 and performance is acceptable now.
However if this 88A battery limit is accurate that would be a greater discharge rate that I would like for my battery. Also the controller SEEMS to get warmer for less acceleration.
Over time I will be able to measure and gather better data. Edit: My method turns out to be : Set battery and phase (1:1) current limit to my battery discharge limit then increment phase current limit till take off torque is acceptable.
John in CR's method:
Step 1:
-Set battery current limit to something modest (low power)
-Set phase current to the same value (1:1 ratio)
Step 2:
-Apply 100% throttle and see how the motor spins up in free air
-Ride to feel what take off and top speed feel / sound like
-Increase only phase current a small step
Repeat testing and increasing phase current until the motor sounds and feels to be powered properly.
Do not expect powerful acceleration yet.
Step 3:
Note the ratio you have reached and increase BOTH battery and phase currents while maintaining that ratio found in Step 2.
I have an 18 FET 4110 and it came from factory with a 65A battery limit, and a 2.8 Battery to Phase ratio. My motor is a "1500W" 10" Scooter motor with a kV of 16.5ish.
I was unable to notice any starved properties at 1:1 (60A, 60A) other than it barely produced any torque. Free air spin up seemed the same.
I reached a ratio of 1:1.5 battery to phase where I could actually move around. I decided at this point to use this ratio to up my battery and phase amps.
I am now at 88A battery with a battery to phase ratio 1:1.55 and performance is acceptable now.
However if this 88A battery limit is accurate that would be a greater discharge rate that I would like for my battery. Also the controller SEEMS to get warmer for less acceleration.
Over time I will be able to measure and gather better data. Edit: My method turns out to be : Set battery and phase (1:1) current limit to my battery discharge limit then increment phase current limit till take off torque is acceptable.
John in CR said:The way I do it is to first determine the proper ratio for that motor controller combination. Set the battery limit at modest power and set the phase limit the same, 1:1 ratio. No field weakening or overspeed settings. Spin it up no load, and also give it a road try up to max speed, so you can hear and feel what the motor is like when starved of phase current on takeoff and at the top end. Often it won't even spin up to full no-load speed. In small increments increase phase current until it doesn't sound or feel starved of current, but you're not looking for hard launch yet. Once it seems to be functioning and sounding correct at that modest power level note the phase:battery limit ratio. Now start turning both up at the same time and maintaining that ratio until you get to the desired power and thrust on takeoff that you want. The end result will be higher power than you had the other way, but the motor and controller will be less stressed, ie less heat, especially under load at lower rpm. FWIW, Zombiess used a similar approach to come up with a 1.8:1 optimum ratio for his 4t Cromotor.