e-bike/moped motor and controller questions

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e-bike/moped motor and controller questions

Postby Mad Professor » Mon Feb 20, 2012 2:36 pm

Good day all.

As per the title I am looking for info regarding e-bike/moped motor and controller.

Most e-bike's & e-moped's I have seen on the internet use DC brushless 3-phase hub motors.

I am working on a e-moped, but the hub motor only has two wires, so can not be a 3-phase brushless motor.

This e-moped works ok on the flat once it's upto speed, but is useless from a standstill, or to try and go up any kind of hill.

I have looked all over the hub motor for a make / model number, the only thing I can see is a name: (TIANNENG), and what I would guess to be a serial number.

The motor is ment to be around 200W so I know it's not very powerfull.

But I was expecting better out of this e-moped.

The controller is very small and light weight, the lable is mostly in chinese, but the model number is: ZKC3615KA-CT2.

There are quite a few wires connected to this box, power, motor, throttle, speedo, etc.

When the motor is free running the voltage at the motor runs from 0-36volts, and pulls around 0.50-0.60amps.
When you try to pull away at a standstill the voltage shows 17volts at the motor, and pulls around 13.40-13.50amps.

13.50A * 17Volts = 229.5Watts, So the motor is pulling alittle bit more then it should.

If the motor is rated at 200W @ 36V, it should pull around 5.555Amps at full voltage.

Is there anything I can do to give this motor more torque at standstill?

Thanks for your time.

Best Regards.
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Re: e-bike/moped motor and controller questions

Postby Drunkskunk » Mon Feb 20, 2012 3:39 pm

Unfortunatly, not much.

And welcome to the forum.

The 200w rating is the nominal rating, what it will pull when running at normal speed on flat ground. It should normaly be pulling 500-750 watts under acceleration. But you have a battery problem. The batteries should not be sagging down to 17 volts under a 750 watt load. Idealy, they shouldn't be dropping much under 36 volts, even under load and half discharged.

A battery actualy able to handle the load would give you 2 to 3 times more torque off the line and up hills, but even that would be anemic. It won't cost much more to get a 500w brushless motor and controller, matched with a good battery.
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Re: e-bike/moped motor and controller questions

Postby Mad Professor » Mon Feb 20, 2012 4:17 pm

Thanks for your reply.

For my test I had three DVM connected, two for voltage and one for current.

Battery pack voltage was always around 33-37Volt even when the motor was under load, when the motor was powered at standstill the readings was: 13.50Amps & 17Volts at the motor.

Here is a quick YouTube video of testing the motor.


Also I am limited to a max of 200W

Quote from Wiki - Electric bicycle laws
United Kingdom

Despite the more recent EU directive and standard, the UK’s Electrically Assisted Pedal Cycle Regulations 1983 (SI 1983/1168) have not been rescinded and still apply. These require that the motor has an average power output limited to 200 W (250 W for tricycles and tandems), weight limited to 40 kg (60 kg for tricycles and tandems), and a maximum speed when power-assisted of 15 mph. For electric cycles meeting these requirements, the vehicle does not require registration or periodic road worthiness assessment, and operators do not require a licence or insurance. (Operators must be at least 14 years of age.) However, since 2006, when Statutory Instrument 2935 brought EU Directive 2002/24/EC into UK law, vehicles that don't meet the EU definition of an electric cycle have required type approval. This overlap of requirements has certain effects, as described below.

The following features of a EU-definition electric cycle are not legally available in the UK:
upper power outputs between 201 W and 250 W on bicycles
maximum speeds between 15.01 mph and 15.53 mph
weights above 40 kg for bicycles and 60 kg for tricycles and tandems

The following features of a UK-definition electric cycle make a vehicle subject to type approval:
the application of motor power without use of the pedals
the application of motor power without progressive reduction to zero at 15.53 mph (meaning that at the maximum UK speed of 15 mph some residual supply of power is permitted)

There are no known cases of enforcement of the requirement for type approval. This could be because compliance with type approval is declared when a vehicle is first registered for use on the road, and UK-definition electric cycles are exempt from such registration by the 1983 UK regulations.
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Re: e-bike/moped motor and controller questions

Postby Drunkskunk » Mon Feb 20, 2012 4:54 pm

I see. I assumed you were reading 17 at the battery. As long as the battery voltage is staying up around 36, then its doing good. Seeing the 17v in this case is likely a result of the controller cutting back to comply with the 200w peak (and failing to do so in your favor).

If you want to comply with the letter of the law, you won't be able to improve the performance with that motor. a gear drive would give you a little better low speed torque, but would need a radicle change in the bike.
Most simply choose to follow the spirit of the law. If you ride responsably, it doesn't matter if you have 200w or 2000w available. Laws are ment to weed out the irresponsable.
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Re: e-bike/moped motor and controller questions

Postby d8veh » Mon Feb 20, 2012 7:05 pm

You're limited to 250w in the UK. The current state of the regulations is extremely complicated.
The 250w is the rating of the motor. The max power for a short time is not specified in the regulations, consequently most 250w motors make about 700w max, or you can say that they draw about 15 amps at 36v, which is close to what you're getting.

Your problem is that the batteries are shagged and can't provide enough power. Get some more batteries. I'm assuming that they're SLAs rather than lithium, in which case make sure that you get the type for electric vehicles that can give more current without the voltage going down.

There's one more thing you can do to get more pulling power and that's to solder the shunt in the controller. The controller uses the shunt to see how much current it's giving and it'll be limited to about 13 amps. If you open up the controller to find the shunt that looks like a small piece of coathanger wire and solder all over it's surface for about 1/3 of its length, the controller will then give more current - say 16 amps. Don't do this without getting new batteries. There's lots of info about soldering shunts here and on the pedelec.co.uk forum - just do a search.
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Re: e-bike/moped motor and controller questions

Postby dogman » Tue Feb 21, 2012 7:52 am

If the battery sags from 37v to 33 v under only 250w load, that's not a good sign.

But the bottom line is, 250w doesn't do much. So don't expect much out of it. The only way to get better performance is going to be a start over, using something much better. 1000w is pretty nice. 3000w is really nice. Whether you can get away with it in your area is your call.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE

Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum

See battery technology section, FAQ thread at the top of the page for lipo noob info.
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Re: e-bike/moped motor and controller questions

Postby Mad Professor » Fri Mar 02, 2012 5:26 am

Regarding the voltage drop, it seems that I am getting alot of voltage drop over the power feed cables from the battery pack to the controller.

Testing the voltage drop with a DVM and I get the following.
Negative: 0.3volts drop @ load.
Positive: 2.0-2.3volt drop @ load.

So a total of 2.3-2.6v drop just over the power cables.

What size cables should I replace the old ones with?
I was thinking something like, 4mm2 (38A) or, 6mm2 (50A).
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Re: e-bike/moped motor and controller questions

Postby docnjoj » Fri Mar 02, 2012 9:31 am

You could double or tripple the wire that you have or replace it with thicker copper. This will help a bit but the main criterion for the wire is "Does it get warm or hot?" If it does replace it. It will make a bit of difference but not a whole lot. Welcome to the sphere.
You will need to upgrade as others have suggested to get much more performance.

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