Can my hub motor and battery handle this?

[zooz]

Hi people,

I have a kit from BMSBattery - http://www.bmsbattery.com/ebike-kits/345-bafang-350watts500watts-bpm-motor-e-bike-kit.html . It is 36V 350W Bafang BPM front drive hub motor with 450W KU93 controller and a 36V11Ah LiFePO4 battery pack - http://www.bmsbattery.com/36v/326-24v-lithium-ion-little-frog-abs-shell-ebike-battery-pack.html .

So I am just wondering if I could replace my 450W controller with a 500W KU123 controller from BMSBattery? Will my battery be still able to coupe with the load? And will my motor not explode due to increased power?

Thanks in advance!

- zooz

 

[tony67]

It will work fine but don't waste your money, you wont even notice the difference. Im not sure what current those controllers actually draw but the sums say 450w draws 12.5 amps and 500w draws 13.8 amps (@36v). If those currents burn out your motor it is better off in the bin.

If your after speed, increase your voltage. If your after acceleration, increase your amps. Have a root around on here and see what the motor will take in terms of watts, 800-1000 should be do-able. Then get a controller that will give you that.

If you keep everything as is and change the controller, a new 25 amp controller @ 36v will give you 900 watts. Research what the motor will take I'm just guessing @ 800-1000 watts based on other small geared motors.

 

[DCMotorworks]

Agreed. the max discharge rate of your battery is listed at 20 amps so about 750 watts is your theoretical limit.

be aware of the potential for catastrophic front fork drop out failure at higher power levels. The numbers are somewhat debatable but general advice seems to be that front hub motors over 500 watts require steel non suspension forks w/ adequate torque arms installed to be safe.

DC

 

[zooz]

Great. Thanks for your answers.

 

[Drunkskunk]

Generaly those "1000" watt controllers are set at 22 amps, such as the Inferon controllers (48V X 22A = 1056W) That 22 amps would eat your poor battery alive. That battery is only rated for 10 amps continous, 20 amp burst.

The motor could probably take it. I have a similar motor, and wouldn't fear running it to 1000 watts on occasion.

A 12 FET controller would be overkill. 6 FETs could handle far more power than that motor would survive

 

[d8veh]

You cannot use the KU123 controller with that battery. As soon as you hit full throttle, you're battery will cut-out (assuming it has a decent BMS). The 500w rating is a nominal rating for continuous power, but it can draw more than 1500w from the battery at full throttle. They're set to 30amps max. You're also pushing it a bit with your KU93 controller. Mine draws about 25amps, which is too much for a 12aH LiFePO4. It'll work, but it'll wear out your battery quickly aand then you'll start getting cut-outs at full throttle. If I were you, I'd get a wattmeter so that you can file the shunt in the controller to limit it to about 20amps, or get a Speedict or Cycle Analyst that can do it by software.

 

[d8veh]

Just noticed that it's a front BPM motor. I've fitted three of those to front forks and they're still going strong after about a year with no problems; however, it isn't always easy - as others have found out. If you could post a picture of your drop-outs or forks, we can advise you on how to do it successfully. From my experience the KU93 is a perfect match for the front BPM. What code number is written on yours. If it'sa code 15 you might find it a bit slow at 36v.

 

[zooz]

Just noticed that it's a front BPM motor. I've fitted three of those to front forks and they're still going strong after about a year with no problems; however, it isn't always easy - as others have found out. If you could post a picture of your drop-outs or forks, we can advise you on how to do it successfully. From my experience the KU93 is a perfect match for the front BPM. What code number is written on yours. If it'sa code 15 you might find it a bit slow at 36v.

I will post some pictures as soon as I get a chance. I installed a torque arm as well as some additional washers, seems to be holding up pretty well. I have done about 200 miles in London already, no problem.

It is a code 13 front BPM motor. I am pretty heavy rider, so it is kinda slow anyway , but pushes me up the hills pretty good.

Thanks.

 

[cal3thousand]

Wouldn't it be better and more cost effective to just put some solder on the shunt?

 

[chvidgov.bc.ca]

I am able to pull over 30 amps from my KU123 controller. That is overkill for a smaller 11 Ahr battery, unless the C rate is around 3C continuous rating, like a Headway pack.