36v 48v controller on 36v battery for ebike

[kukrimaster]

Dear all brothers and sisters out there.. I am a noob on ebike and electronics. I just acquired and ebike and after having suggest by the repair shop to upgrade my controller from 36v to a 36v/48v compatible controller and changing of sensors, the controller is suppose to support up to a 48v battery. However, I noted that after change of the controller, my usual speed of max 25km per hour had drop to only 18km per hour.

The shop keep asking me to change to 48v battery which I am quite hesitant. Is it normal for the speed to drop if the controller had been upgraded without upgrading the battery? My motor is the 36v brushless motor.

All advice are welcome.

 

[amberwolf]

The speed should be the same, if all else is the same, and the new controller is at least as good as the old.



What "sensors" did they change?

If the speed dropped when controller was changed, but all else is the same, and you are using the throttle the same way, then the most likely problem is either:

-- the new controller has a speed limiter,

or

-- the new controller has a lower current limit than the old, so it can't provide enough power to move you as fast.


To test whcih one, flip the bike upside down, and run the motor at max throttle. (the speed sensor has to be on the powered wheel for this)

If the speedometer reads the same slow speed as it did when riding, then the first is true.

If the speedometer reads a little faster than you used to be able to go with the old controller, then the second is true.


For either one, there could be settings that can be changed, but you'd need to ask the place that sold the controller for the manual on how to do that, if they'll tell you.

What it sounds like to me is that they sold you a controller they *knew* would be slower, just so they could then sell you a battery to make it faster again. (and they'd have to remove any speed limits it has when they change the battery. If it's a current limit instead, they'd have to change that too, or it still wont' go as much faster as it could).


One other possibility is that they have gotten the phase/hall wiring combo wrong from controller to motor, whcih can make a motor run slower (and hotter!) but still work (most wrong combos don't work at all, but false positives can).

 

[kukrimaster]

Hi

Thanks for your advice. I do not have sensor for the speed test. Only I can see on my garmin watch during riding. I guess the China man shop is trying to make me buy new battery. The battery if buy a 48v will cause a big modification which can be caught by the authorities on the road. Hence my hesitation. Changing internal parts can't be inspect externally. Modify battery will be an extension of another battery pack which is illegal in my country.

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