48v kit to 72v,

[lotrwiz]

hi. I have a 48v 250w front brushless hub motor kit from 8funbike. its great.

I get 20-18-15-13-8 mph on a charge (thats decreasing over time)

I get around 15-30 miles range on throttle only.

I weigh about 70 kilos and the bike between 20 and 30.

I was wondering, in order to get more speed, could I attach another battery to the frame and motor, in order to have a 72v system. ofcourse I would need a new controller. any suggestions as to which? would I need a new throttle?

also, do you think it would fry my motor?

thanks guys!

I'm aware it wont be a masive increase as its a small motor, but its all that's legal in the UK.

 

[ken1645]

I can answer a couple of these..

I was wondering, in order to get more speed, could I attach another battery to the frame and motor, in order to have a 72v system. ofcourse I would need a new controller.

Yes. Higher top speed comes from higher voltages. Higher acceleration comes from higher amps from the controller.

would I need a new throttle?

No.

 

[Drunkskunk]

hi. I have a 48v 250w front brushless hub motor kit from 8funbike. its great.... do you think it would fry my motor?

Lets put it this way, KFC may be knocking at your door for the recipe!

 

[arkmundi]

You risk melting something inside the motor if you over-amp it beyond its rated tolerance. There's some give, but you'd have to guess how much. Take a circuit, any circuit, like a 100 watt light bulb. Snip the wire and replace it with half its gauge, say from 8 gauge to 16 gauge. Notice that the wire will heat up, because there's more resistance to current flow. That's your motor. If you try it, you may want to add a thermistor to the circuit.

 

[dogman dan]

It won't fry your motor unless you ride it. :wink:

In general, 48v is already kind of pushing these motors. But if you are super careful, and never use much of that 72v, it could be done. But if you can't use it, why spend the money to have it?

Get something in a direct drive motor for overvolt fun. If you have a motor running 48v, then go to 72v, you typically get more speed for sure. The more volts, the faster the no load speed of the motor. Other factors may limit the increase to less than you calculated. But enough volts to make your 8 fun motor go 30 mph, is taking a chance with cooking it.

You could increase volts, but at the same time decrease amps, keeping watts similar. But then the performance increase is pretty lackluster. Most direct drive motors can handle 2000w or so, much more than the geared ones because they shed excess heat a bit better. So go dd for more amps and volts, to have real power. 2-3 hp of 72v is very perky.