Bafang 750w = 33 km/h?

[marcoredit]

Hi,

I have a bafang 750W mid 48v with a li-ion battery (Samsung 18650) 14s. 15.4 Ah.

I'm surprised that the max speed is only 33 km/h. I expect more!

Do you know why? I have to change something?

bike + me = 100kg --- no hills

I regulate all the setting from the Lcd display.

Thx.

Mark

 

[DAND214]

Need more info than your weight.
Gears used, wheel size and I'm sure there will be more requests.

Dan

 

[marcoredit]

you are right.

wheel size is 26.

front gear 42 teeth
rear gear 18 teeth

 

[Sunder]

Something's not right here. Are you talking about the BBS02? That spins at 90rpm from memory.

Let's do the maths:

Motor speed 90rpm.
Front to rear gear ratio = 42/18 = 2.3*
Rear wheel speed = 2.3* x 90 = 210rpm
Rear wheel circumference (Depends on tyre size) 2.0m
Speed = 2.0m x 210rpm x 60minutes = 25.2km/h

Those numbers assume a 36v running at 36v, or a 48v running at 48v. If you're running a 36v at 48v, then your numbers should give you a final speed of 33km/h, which is what you've claimed. Can you confirm you're over-driving your motor? Or is there actually something we've missed/you're not telling us here?

Either way, it's your rear gear that's causing you the problem. 18T is a pretty low final gear. I run an 11T. If you did, you'd get 42km/h. More common is either 12T or 14T. You can do the maths for those two.

 

[teslanv]

Me: 12S Lipo, 50.4 Volts HOC. 26" Wheels, 11T rear Sprocket, 48T Chain Ring (Which is the standard on the 750Watt BBS02 BTW) I easily get 31 mph (50 KM/h) on the flat. Pedal RPM should be close to 100 RPM at Full Throttle.

 

[d8veh]

It could be software restricted. Put a second magnet on the wheel. If your max speed is halved, it's software, otherwise you have to sort out your gearing.

 

[neptronix]

If your only rear gear is an 18T, then that's no surprise.

Most definitely need a lower tooth count rear gear.