3kw motor peak power?

[Cam3roon2k41999]

Hi, my motor is a 3000w 72v kit from solos bikes and I'm running a 60v battery that fully charges at 71.4v, peak Amps is 90a. My controller is 60a so that must mean 71x60=4260, but I get around 8000w when climbing a hill or accelerating is this OK for the motor to run at this power? Also I was thinking of getting a 150a sabvoton controller but that would mean I'll get 10,650w and that seems a bit too much power? Would it explode? Thanks

 

[soundwave]

if you pull to many amps from the batts rated output it will heat up and explode in a ball of flames.

peak amps is not continuous power so if you try to run at 90amps the batt could fail.

 

[vfr400]

Hi, my motor is a 3000w 72v kit from solos bikes and I'm running a 60v battery that fully charges at 71.4v, peak Amps is 90a. My controller is 60a so that must mean 71x60=4260, but I get around 8000w when climbing a hill or accelerating is this OK for the motor to run at this power? Also I was thinking of getting a 150a sabvoton controller but that would mean I'll get 10,650w and that seems a bit too much power? Would it explode? Thanks

Your calculation is not correct for several reasons:

Firstly, your battery voltage drops pretty rapidly initially, so the 71.4v is not realistic. You'd probably lose one or two volts before you could draw any meaningful power from it.

Secondly, you get voltage sag. The battery voltage goes down in proportion to how much current you take from it. I can imagine losing 6v at 60 amps. This would mean about 64v when you fully open the throttle, which would be 3840w from the battery,

but thirdly there is a switching loss of about 5% in the controller, which takes it down to 3648w.

Fourthly, the back emf from the motor reduces the current going through it in proportion to speed. At zero speed, there is no back emf. At max speed, the back emf blocks all the current. Basically, you only get the max current at low speed. If you used a wattmeter, you'd see how much power was coming out of the battery at at any time.

 

[Cam3roon2k41999]

Your calculation is not correct for several reasons:

Firstly, your battery voltage drops pretty rapidly initially, so the 71.4v is not realistic. You'd probably lose one or two volts before you could draw any meaningful power from it.

Secondly, you get voltage sag. The battery voltage goes down in proportion to how much current you take from it. I can imagine losing 6v at 60 amps. This would mean about 64v when you fully open the throttle, which would be 3840w from the battery,

but thirdly there is a switching loss of about 5% in the controller, which takes it down to 3648w.

Fourthly, the back emf from the motor reduces the current going through it in proportion to speed. At zero speed, there is no back emf. At max speed, the back emf blocks all the current. Basically, you only get the max current at low speed. If you used a wattmeter, you'd see how much power was coming out of the battery at at any time.

Thanks for the info I did not know that lol
But how come my SW900 says I'm output 8000w up a slight hill and on normal flat I get around 5000-5600w full throttle it's brain baffling

 

[Cam3roon2k41999]

Also I had a voltmeter and it dropped from 71.4v to about 68.9v when full throttle so does that mean I'm running too much power as I weigh 19stone and the bike weighs allot and still achieve 51mph lol

 

[vfr400]

Also I had a voltmeter and it dropped from 71.4v to about 68.9v when full throttle so does that mean I'm running too much power as I weigh 19stone and the bike weighs allot and still achieve 51mph lol

The faster you go, the better it is for the motor, but might not be better for you. You'll see that the voltage drop at full throttle is a lot more when you're going slow compared with when going fast.

Your SW900 is probably using the wrong value of the shunt or something like that to calculate the power. Did it come with your controller or did you buy it separately?

 

[Cam3roon2k41999]

The faster you go, the better it is for the motor, but might not be better for you. You'll see that the voltage drop at full throttle is a lot more when you're going slow compared with when going fast.

Your SW900 is probably using the wrong value of the shunt or something like that to calculate the power. Did it come with your controller or did you buy it separately?

Yes the SW900 came with the controller.