Traction problem with Big Bear

[Marwood Hill]

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

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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[Marwood Hill]

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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[Deleted member 4366]

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.

 

[Woosh]

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.

 

[Woosh]

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.

 

[Marwood Hill]

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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[danielrlee]

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.

 

[Marwood Hill]

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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[Deleted member 4366]

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.

 

[Marwood Hill]

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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[Deleted member 4366]

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.

 

[Marwood Hill]

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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[anotherkiwi]

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

 

[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

Thank you, that looks just the job.


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[Deleted member 4366]

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

 

[Marwood Hill]

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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[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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[Woosh]

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.

 

[Marwood Hill]

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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[Woosh]

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.