help making the ebike pedal assist?

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jlatshaw   1 mW

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help making the ebike pedal assist?

Post by jlatshaw » Jul 27 2013 8:16pm

Hello,

I am thinking of a design for an ebike, and I would like to have the option to have the bike powered by either pure pedal, pure motor, or a mix between the two.
In other words, I need the power delivered from the motor to be independent of the power delivered from the pedals so I can choose to pedal, use the motor, or a mix at any time.

How do people normally go about doing this for a bike powered by an electric motor?

Is there such a thing as an (affordable) dual freewheel sprocket (two independent freewheels)?
Or can I put two freewheels on the rear hub and hook my motors chain to the one and my pedals to the other?

How should I do this?

Thanks,
-James

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lifepo4ever   10 kW

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Re: help making the ebike pedal assist?

Post by lifepo4ever » Jul 27 2013 9:51pm

there 2 way , the new version of the pedal assist (THUN ) is compatible with the v3 CA you can find it at ebike.ca or use a on\off switch between the pedal sensor (P.A.S) and the controller

d8veh   100 GW

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Re: help making the ebike pedal assist?

Post by d8veh » Jul 28 2013 3:02am

jlatshaw wrote:Hello,

I am thinking of a design for an ebike, and I would like to have the option to have the bike powered by either pure pedal, pure motor, or a mix between the two.
In other words, I need the power delivered from the motor to be independent of the power delivered from the pedals so I can choose to pedal, use the motor, or a mix at any time.

How do people normally go about doing this for a bike powered by an electric motor?

Is there such a thing as an (affordable) dual freewheel sprocket (two independent freewheels)?
Or can I put two freewheels on the rear hub and hook my motors chain to the one and my pedals to the other?

How should I do this?

Thanks,
-James
Most controllers work like that already. You don't have to do anything other than connect it all up, as long as you have a controller with a PAS sensor connector.

The way most of them work is that the motor gives power as soon as you pedal How much power you get depends on the algorithm in the controller software. Some give only maximum power, some give cadence related power (pretty crap), and some are more sophisticated (torque sensor simulation). You also have an independent throttle, and as soon as you use it, it takes precedence over the PAS, so you can use it any time to get whatever power you want.

To me, the best controllers for pedal assist have an LCD display, where you can set the PAS level in five or seven steps. Some of these have level zero for throttle only, which is not so good because you have to select it before you can use the throttle, while as other allow instant throttle

Whichever system you have, there's nothing to stop you putting a switch on the red throttle and PAS wires to disable them for better control.

For a high power motor and pedal assist, you need one of the controllers with the LCD to adjust the level, or a torque sensor system. It's not so important on a 250w system, but always useful to have.

If you described your speed and power requirements, it would be possible to recommend a controller.

jlatshaw   1 mW

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Re: help making the ebike pedal assist?

Post by jlatshaw » Jul 28 2013 11:39am

Thanks so much for those insights.
This is a bit of a custom job so I'll tell you what I have so far and from that maybe you all can help me decide what my next best route is.

Right now I have a 24v 200w-350w motor ( http://zjmy-lu.en.made-in-china.com/pro ... 1016-.html ) which I think will serve well for pedal assist (at least I hope). This motor is suppose to automatically adjust it's current draw to meet whatever load it is faced with, but to help me better control the the motor's output power I plan on using a PWM (Pulse Width Monitor) to control how much current the motor sees and thus its output power and speed. On that side of things I understand and think everything will work out nicely. My problem now is in finding a way to have the pedals and the motor independent of each other.

What exactly do you mean by a controller? How much do they typically cost?

What are also some alternatives?

Finally, is it at all possible to just put two independent freewheels on the rear hub?

Thanks,
-James

d8veh   100 GW

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Re: help making the ebike pedal assist?

Post by d8veh » Jul 29 2013 9:02am

That makes it more difficult. Brushed motor controllers with PAS connectors are harder to find, but they do exist. Perhaps someone can give a direct link.
here's an example of a controller, but this one doesn't have a PAS connector
http://www.aliexpress.com/item/24V-350W ... 47337.html

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middriveebike   100 mW

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Re: help making the ebike pedal assist?

Post by middriveebike » Jul 29 2013 9:50am

What is the difference when you have pedal assist sensor and without?
Let's say you dont have the pedal assist sensor, can't you just pedal and use throttle to control the motor at the same time?

jlatshaw   1 mW

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Re: help making the ebike pedal assist?

Post by jlatshaw » Jul 29 2013 6:45pm

I understand how to control the speed to the motor, however I am not asking how I can control the speed of the motor.
I am asking how can I keep the power from the motor separate from the power from the pedals?

d8veh   100 GW

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Re: help making the ebike pedal assist?

Post by d8veh » Jul 30 2013 4:51am

Sorry, you've lost me completely with that one. I can't understand what you want. Have a read of my first post above and tell me how you want your bike to be different.

With the motor you've chosen, you've made it tricky. Most people would use a brushless hub-motor and a brushless controller with PAS.It'll do everything you want quite cheaply.

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alsmith   100 kW

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Re: help making the ebike pedal assist?

Post by alsmith » Aug 18 2013 11:32am

My bike started off that way- 3 position key switch- off, pedal assist, throttle only and a brushed motor. It stopped working just out of warranty failing with full throttle permanently engaged whatever the key position, the only way to stop was to brake as hard as possible then stop with the wheel against a wall while unplugging the battery. So I changed to brushless.
That controller was a proprietary one so expensive for what it was- a tiny UK legal 250W one. It's probably too low on power for you, the manufacturer changed to brushless a while ago so probably have none left, but if you insist try emailing powabyke in the UK- you don't have your location in your posts .....
(add by going to User Control Panel, select Profile in the User Options- it's about 6th or so on the list)

Or try Edward Lyen- he has a pedelec adapter that links to the throttle connector so no need to open and solder your controller. Check with him that it will work with brushed. Lots cheaper than a controller if it will work. And he may have a controller if it won't work.
email: Lyen@hotmail.com

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lollandster   10 W

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Re: help making the ebike pedal assist?

Post by lollandster » Aug 19 2013 11:46am

From what I read in the first post it sounds like you are looking for a way to drive the wheel with the motor without rotating the pedals and/or pedal without dragging the motor. All the answerers above are concerning PAS as your topic title indicates, but if this is not what you are asking for you might want to take a look at www.cyclone-tw.com where they use a motor, similar to yours, connected to a freewheeling bottom bracket.
Disclaimer: I know nothing.
My ebike build blog

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