more amps for a restricted crank motor

[tifalou]

Hello, I have a MBK bicycle with a Yamaha crank motor. Due to the EU regulations, its power is limited to 250W. I am used to ride a bike with an unrestricted hub motor, so the MBK seems rather weak compared to it.
I tried to series a 12V battery to get more voltage (originally 36V), but the system cuts off as soon as it exceeds 42V. Then, I dared to open the controller, in order to add a bit of solder on the shunt. Unfortunately, no visible shunt inside !
I don’t need a dongle, because it would only remove the speed limit. In fact, I would really appreciate to get some more amperes for a higher speed on hills.
Do you know a solution for such an improvement on a prebuilt mid-drive motor ?
Thank you.

 

[wesnewell]

Find the HVC circuit and change it to allow higher voltages. You should also change LVC.
Replace the 36V with a higher voltage controller. Probably the easiest thing to do.
If you do increase voltage, you'll need to make sure you don't burn up the motor.

 

[d8veh]

The speed limit will be controlled by software, so you can't change it with a voltage increase. You need a device that intercepts the speed signal from the wheel and resends it at a different speed. You can get various dongles to do that, but they're expensive.

You get solid state shunts as well as the wire type. They're little black flat devices with something like 001 writen on them. Sometimes there's more than one in parallel either side by side or stacked. When you know their values, you can change them by stacking another.