Electrical/mechanical question

[Fimka]

Hi,

Whats the math/calculation behind figuring out how much power the motor will draw from the batteries based on the currest setup. what factors should be considered (eg. weight, RPMs, etc.)

As an example my current setup:
Motor: 36v, 500w, 3000 rpms max
Controller: 36v, 500w, 30amps
Kart weight: 100lbs
Rider weight: 180lbs

Also, is there a way to figure out how much the motor will take, if i reduce the gearing form 6:1 to 4:1 what's the math in figuring out if your engine/controller will be able to take it

Any help is appreciated

Thanks

 

[landuse]

Hi there. I am not too sure of all the maths, and there aren't too many forum members who work with electric, so you might have to wait a little bit longer for someone to answer you. The will though.

I hope you find what you are looking for. Do a search or read the electric section of the forum. I am sure someone asked this same question not too long ago.

 

[jman231994]

Ok, that motor should be drawing 13.9 Amps when at full load (500w) Most however are capable of going over their full load. I have no idea what it will peak at, but lets sat 850w. At 850w it would be drawing 23.6 Amps. I get this by using this formula P=IV, if you rearrange that you get I=P/V, P being power in watts, I being current in Amps, and V being volts.

To work out your speed and load with those gearings I'll need to know your wheel size, and even then I dunno if I can work out the load. I can try though.

My friends and I built an electric bike for a comp last year and we used a 500w motor. Ours all up weighed around 90kg, which is roughly 30kg lighter than yours. Quite simply, it was atrocious. Nowhere near enough power for the weight and we struggled to go fast enough to qualify. I really recommend staying with 6:1 at least when trying to move that much weight. To put it in perspective, around 740 watts is equal to 1 horsepower. So you are working with much less than 1HP.

If you have any more questions I'm happy to help