the motor's 3 phases have to be sync'ed to the position of their magnets. If you have two motors, there is no simple way to lock the position of the magnets on the front motor to the rear motor. That's why you have to use a specialized controller that has two motor cables.

 

http://www.szktdz.com/en/news_show.php?article_id=523

 

http://www.szktdz.com/upload/image/20170527/20170527084352_29295.jpg

 

Thanks for this. Sounds good. I am at present fitting the new back wheel motor. I will test it out on our steep hills. I know before i even fit it that its going to be so much better than front wheel drive.

 

 

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If i fitted this switch to enable front or rear wheel drive would there be any loss of power due to current running through this generator switch?

 

 

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You need a switch with a rating of at least 30 amps. To run two motors, you need two controllers, two throttle, two pedal sensors and two displays.

 

If you only wanted to run one motor at a time, it could be done with one controller, but you'd need a 3-phase switch.

If i fitted this switch to enable front or rear wheel drive would there be any loss of power due to current running through this generator switch?

 

 

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the loss through this kind of switches is very little.

I would test first with manual connection/disconnection before going ahead with the switch.

You need a switch with a rating of at least 30 amps. To run two motors, you need two controllers, two throttle, two pedal sensors and two displays.

 

If you only wanted to run one motor at a time, it could be done with one controller, but you'd need a 3-phase switch.

I did recommend using anderson connectors as an alternative to 9-pin two position switch.

Thanks for the tips. I have got the rear motor all fitted and running smoothly. I haven’t yet tried it on our steepest hills. It’s just that i’m now looking at that lovely BPM motor in the front wheel disconnected and not doing anything. Anyway, finding a 3 phase smallish 2 way switch in a weatherproof housing is almost impossible . And i don’t really know if it would be beneficial having a dual motor bike using either front or rear wheel drive. Cannot run two together as it would not be road legal.

 

 

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Edited December 15, 20178 yr by Marwood Hill

I fail to see the point of a dual motor setup that cannot be operated as 2WD. The only benefit would be redundancy, which might be desirable on a long distance tourer. With such a setup you'll always prefer to use the rear motor anyway.

 

'Legal' is overrated. Give each motor its own controller and the dual motor setup becomes worthwhile.

You need a switch with a rating of at least 30 amps. To run two motors, you need two controllers, two throttle, two pedal sensors and two displays.

.

 

How would i fit brake lever cut-out switches for two motors?

 

 

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How would i fit brake lever cut-out switches for two motors?

 

 

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Both controllers need a common ground, then you connect the brake switch ground to any ground and split the signal wire into 2 - one to each controller's brake signal wire.

Thanks for all this info. I’ve decided that i don’t want permanent 2 wheel drive. I only want to bring the front motor back into use and use 2 wheel drive only when i’m pulling my loaded trailer uphill and pulling it on grassy areas. Does anyone know of a UK stockist of bike build bits? Ebay is ok for throttles but not much else.

 

 

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To work both motors at the same time, you'll need an additional battery and controller. Your battery can't supply enough power for two motors. You have the option of replacing your present battery with a high power (40A minimum) one. If you want to do the wiring, both controllers can share the same throttle, pedal sensor and brakes.

To work both motors at the same time, you'll need an additional battery and controller. Your battery can't supply enough power for two motors. You have the option of replacing your present battery with a high power (40A minimum) one. If you want to do the wiring, both controllers can share the same throttle, pedal sensor and brakes.

 

Thanks. So all i need is a battery with an integrated controller housing and fit it to my front rack. As it’s only for occasional use i won’t need an expensive high power battery. Perhaps a bottle battery with controller. Any idea where i can source one when i’m ready to buy?

 

 

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Edited December 16, 20178 yr by Marwood Hill

https://bmsbattery.com/ebike-battery/675-36v116ah-bottle-ebike-panasonic-battery-battery.html#/27-ac_voltage-200264vac/323-controller-s06s_hall_sensor_sine_wave

https://bmsbattery.com/ebike-battery/675-36v116ah-bottle-ebike-panasonic-battery-battery.html#/27-ac_voltage-200264vac/323-controller-s06s_hall_sensor_sine_wave

 

Thank you, that looks just the job.

 

 

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Thank you, that looks just the job.

 

 

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If you have a hall sensor motor, you should get a controller for hall sensor motors. That one is for sensorless motors. Some BPMs have sensors and some don't. Which is yours.

 

https://bmsbattery.com/ebike-battery/679-36v125ah-bottle-09-e-bike-battery-pack-battery.html

If you have a hall sensor motor, you should get a controller for hall sensor motors. That one is for sensorless motors. Some BPMs have sensors and some don't. Which is yours.

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The link to battery with integrated controller gives option of controller. I don’t know which Big Bear BPM mine is at moment?

 

 

 

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Edited December 16, 20178 yr by Marwood Hill

The link by anotherkiwi to battery with integrated controller gives option of controller. I don’t know which Big Bear BPM mine is at moment?

 

 

 

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The link to battery with integrated controller gives option of controller. I don’t know which Big Bear BPM mine is at moment?

Both your front and rear motors are sensorless.

The motor cable has 3 pins.

Both your front and rear motors are sensorless.

The motor cable has 3 pins.

 

Thanks for this info. I’m gradually learning what i will need. When it’s done it probably won’t be as complicated as it seems at the moment. All them wires coming out of a controller and finding out which goes where will be the biggest challenge.

 

 

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When it’s done it probably won’t be as complicated as it seems at the moment. All them wires coming out of a controller and finding out which goes where will be the biggest challenge.

You are too modest, you did fine so far all by yourself.

You are too modest, you did fine so far all by yourself.

 

Thank you Woosh. And thanks for supplying the new rear wheel with motor. The Big Bear is now even bigger. What a bike it would be with 2 wheel drive option but i’m thinking that another £300+ for battery / controller would be just too much at this time. I may just fit connectors as you suggested. Who knows, a bargain price for all the extra bits to make it 2 wheel drive may come along one day.

 

 

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I think the easiest/cheapest way to make a 2WD is to fit a dual motor controller. KT may supply you one for sensorless motors. You would also need to replace the King Meter JLCD with one of theirs.

 

http://www.szktdz.com/en/news_show.php?article_id=523

I think the easiest/cheapest way to make a 2WD is to fit a dual motor controller. KT may supply you one for sensorless motors. You would also need to replace the King Meter JLCD with one of theirs.

 

http://www.szktdz.com/en/news_show.php?article_id=523

 

This looks good. Scratching head, a lot of wires and housing it could be a problem. Would this just use my existing one battery?

Has anyone ever ridden a dual motor bike? Imagine i’m struggling uphill pulling my trailer using my existing rear wheel drive. If was able to activate the 2 wheel drive would this help on the hills?

 

 

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I've built several bikes with two motors and one with three. Traction is their main advantage, but only when you use low-power motors. if the back one gives too much torque, it unloads the front one and makes it spin or skip, like you had before.

 

Like I already said, your battery isn't strong enough to work two motors. you need one that can supply 40 amps or more continuous.

Like I already said, your battery isn't strong enough to work two motors. you need one that can supply 40 amps or more continuous.

 

that KT09S2 outputs 2 x 17A, I specified the Big Bear battery with a 30A BMS.

 

This looks good. Scratching head, a lot of wires and housing it could be a problem. Would this just use my existing one battery?

Has anyone ever ridden a dual motor bike? Imagine i’m struggling uphill pulling my trailer using my existing rear wheel drive. If was able to activate the 2 wheel drive would this help on the hills?

 

 

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Nobody I know besides d8veh has built a dual drive. However, the wiring of the KT09S2 is similar to the Lishui LS947 on the Big Bear. Yes, you should be able to run the bike on the same battery if you so wish, albeit 2 x 17A = 34A, the BMS may trip.