motor torque

[ianrodness]

Hi everyone
I've recently purchased an EB electrobike as my entry into electric cycle world. I'm enjoying it so far, but have one concern. The bike is equipped with a 350w brushless motor, and 36v lead acid battery pack. On the downhills it gains quite a bit of speed, and on the flats, requires pedal assist (I enjoy the excercise). The problem I'm having is on the uphills - any kind of uphill. The motor seems to completely lack any kind of power in this situation. Is there anything to be done to improve the torque of the motor without buying a new one. Is it possible to clean the motor?
thanks for your help

ian

[Patriot]

Increase the voltage going to the motor, by getting a differant battery, or rewiring the one you have to put more of its cells in series. You will lose range when you do this though.

Make sure you have a heavy duty 72v controller. You can double your voltage up to 72v, and get much better performance, along with alot more speed.

[cerewa]

how many amp hours are your SLA batteries?

In short,

more voltage = more speed
more amps = more torque


the amount of torque you get from a particular motor is dependent on the number of amps, not the number of volts. Because the torque of your motor seems to be so low, I am guessing that the problem is the controller's Amp limit. If you have low amp-hour batteries (say, less than 15Ah) then it's possible the batteries also can't handle more amps, but the most likely problem is the amp limit on the controller.

In any case, if a motor has too little torque and more top speed than is needed, the thing that will give it more torque and less top speed is to lower the voltage and raise the number of amps.

If a motor has too little top speed and more torque than necessary, you can give it more top speed and less torque by reducing the number of amps and increasing the voltage.

The reason Patriot's answer works, to some degree, is that more volts at the same number of amps will increase the amount of power coming out of your batteries. The raw power will help you get more torque a little bit but most of the energy from the excess voltage is turned to heat (wasted). If the resistance in your motor is so high that you can't get reasonable torque out of it without raising the voltage, either 1) your motor is a bad design or not being used for what it's made for or 2) your motor's broken.

[ianrodness]

okay - good info cerewa. As i'm new, is it an easy task to calculate amps, and amp hours? Is that kind of info printed on the batteries, or do I need a multimeter to figure it out?

[ianrodness]

eb jazz

[cerewa]

As i'm new, is it an easy task to calculate amps, and amp hours?

pretty easy, yes. Your motor+controller are apparently rated at 350watts@36 volts together. volts * amps = watts, so that means that your controller is supposed to put up to 10 amps * 36 volts through the motor. That's probably a "continuous" rating, meaning if you go uphill at full throttle for just 30 seconds your controller is probably made to consume up to 15 amps. So if you wanted a lot more torque, you could buy a controller made for 36 volts / 30 amps peak or you could set up your bike with 24V batteries and use a controller that can handle 24V / 30 amps peak power.

But what I'm now thinking is that I may be leading you down the wrong path with all this talk of increasing your amps - it may be that your controller (or, not very likely, it could be your motor) is just not working right. Replacing it with an identical controller or getting the manufacturer (or your favorite electrical-engineer friend) to figure out what's wrong with it might just do the trick. I think it's doubtful that one of these pre-made ebikes was built so wrong from the start, unless a one-time mistake in assembly got you the WRONG part (motor or controller) installed on your bike.

[ianrodness]

thanks for your help cerewa, and patriot.
good things to think about, and doing all this research will just help me understand the workings of the bike better. I'll start with getting the controller checked out, and go from there. I'll get back to you if I come up with some good results. If I lived in the U.S., I'd be voting for Obama too.