Shunt Mod on a 3KW Controller?

[Trike-Life]

Howdy everyone. My name's Evan I'm new to this forum, Im from Sacramento. I already introduced myself in that specified introduction section.

I'm pretty mechanical I have a Schwinn Meridian that I am doing a 3kw 72v mid drive motor conversion myself.

I install bought a cheap sine wave controller off temu but the non-sine controller that actually came with the motor and batteries I am beginning to like more, mainly because it has cruise control. And a couple other features that are interesting.

So I was thinking about doing the Shunt Mod to my controller. However I see most videos that show this mod and they're soldering 2 bars together, my controller has 4. So do I solder all 4 together? Please see pic included.

Also check out my Schwinn Meridian and my 3kw motor and 6 12v AGM batteries.

Thanks for any help.

 

[Chumley]

I am new to ebikes, but I had a career in troubleshooting issues with machinery and electronic controls. The Shunt mod alters the current monitoring ability of the controller so that it reads lower current than is actual. So if your controller is delivering what it is reading as 20 amps, it could be actually delivering 40 amps. This is important! While the mod does what is says it does, allowing more current to the motor and phases, it needs components to deliver that current. So unless you increase the wiring size, MOSFET controller Capacity, motor winding capacity, you could easily burn out or set on fire to your motor, wirings, controller....

In addition, the shunts are not just soldered willy/nilly. You need to measure the voltage drop across them, then adjust for a lower voltage drop. If you just solder over the shunt, the controller will read amps that are significantly lower than actual, and probably burn out the controller.

Get a better, higher amp controller, upsize wiring gauges, make sure you know the max eletrical capacity of the motor.FWIW, a 3KW motor is max about 42 amps. So every electrical component should be sized for at least 42 amps. I would add a margin and rate for at least 50 amps @ 72V.

Larger wires will have less voltage drop, so that helps too.

 

[Annieolnie]

Thank you Chumley, great advice!

 

[Trike-Life]

I am new to ebikes, but I had a career in troubleshooting issues with machinery and electronic controls. The Shunt mod alters the current monitoring ability of the controller so that it reads lower current than is actual. So if your controller is delivering what it is reading as 20 amps, it could be actually delivering 40 amps. This is important! While the mod does what is says it does, allowing more current to the motor and phases, it needs components to deliver that current. So unless you increase the wiring size, MOSFET controller Capacity, motor winding capacity, you could easily burn out or set on fire to your motor, wirings, controller....

In addition, the shunts are not just soldered willy/nilly. You need to measure the voltage drop across them, then adjust for a lower voltage drop. If you just solder over the shunt, the controller will read amps that are significantly lower than actual, and probably burn out the controller.

Get a better, higher amp controller, upsize wiring gauges, make sure you know the max eletrical capacity of the motor.FWIW, a 3KW motor is max about 42 amps. So every electrical component should be sized for at least 42 amps. I would add a margin and rate for at least 50 amps @ 72V.

Larger wires will have less voltage drop, so that helps too.

You raise some good points.

I was already looking at this puny wire (on both the controller AND the motor) and was not a fan. These battery and wires appear to be 12 ga, on a good day, probably more likely 14 ga. If I was designing the system from the ground up, I would use four gauge. Do you think if I were to upgrade the wiring even inside of the controller and motor to a thicker gauge wire, I would see more performance?

As much as I agree with you, burning the stuff up does not bother me too much. In the event I do, I'm going to upgrade everything anyway. So therefore a little bit more information about the shunt mod and how to correctly connect those bars, would be greatly appreciated.

BTW my controller claims it's good for 84v and 60a.

Thank you very much for the great information.

 

[Chumley]

Well, I would check ratings on everything. The controller has mosfet transistors to control power to the motor. They have an amp rating. Larger wires help even without increasing amps because they larger wire will have a lower voltage drop. Controllers are relatively cheap. Find one with a 50 amp or better rating. The Motor is the most expensive part after the batteries. The motor will have a shorter life if it is spent in the maximum output mode. So some caution remains.

It's kind of like putting a 1000 hp motor in a Fiat 500. It will accelerate fast, but stopping, turning, handing will all try to kill you because the rest of the vehicle wasn't up tp the power.