how do I reduce power? (sunwin too strong!)

[drifta303]

Hey all I have one of those Sunwin 750w 48v controllers, but it seems to be drawing nearly 3000w (according to my cheap amp meter anyhow the peak amps is around 64 at 48v)

This morning i tried wiring in the low speed setting by connecting the black and yellow wires, i think it has brought it down to about 55amps max but thats still too much for my 1000w hub motor i think..

so is it possible to reduce the power somehow?

either through limiting my hand throttle (adding a resistor?) or by doing the reverse of a shunt mod?

not sure if anyone has done this before but advice would be helpful and appreciated!

Merry Christmas all!
PAul

 

[Ianhill]

There's a guy on the with electric scooters section that does just the thing you mention, he removes the shunt measures its resistance and then replaces it with a piece of cable thick enough to be up to the job of transferring the amps and long enough to bring enough resistance into play so he half's his output to where he wants it simple and effective, so for example if your shunt is 100mohm swap it too 300mohm with 14awg wire and it should put out the 1000w you need.

 

[Samd]

Gday paul I can show you via facebook chat mate. Cheers.


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[e-beach]

You could just use less throttle. Or....

You could get a 3 speed switch. They don't cost much. What it is, is a series of resistors in a potted housing. It cuts the throttle voltage of 5v or so, to a lower voltage depending on the setting. Less voltage from the throttle to the controller reduces amp draw.

Or you can get another controller, something like 48v 1000w.

You could put your own variable resistor inline with the throttle.

You could open your controller and cut the shunt....not recommended by me, but it is a way to hack through the problem.

I vote for getting a new controller.

 

[Samd]

Had five mins. Opened one up.
Yep cut or dremel one shunt.

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[Ykick]

Just a thought? Before you get too far along chomping on things it might be a good idea to check your "cheap" power meter against another Amp meter?

Good thing about power meter is they're pretty much the same "error" whether measuring low Amps or high Amps. That in mind, many DVM's can measure 10A max which should be enough range to test with the wheel off the ground. Wheel off ground should be less than 5A. Compare that to your "cheap" power meter. If in close agreement then you're probably actually drawing 55-64 battery Amps.

But if not, you may wish to dig a little deeper into your power meter accuracy?

 

[dogman dan]

Yeah,, I smell a rat too. Makes no sense at all some 750w controller is putting out that much power. Controller watt ratings seem to have no consistency, so it's quite plausible that it's actually putting out 1500w peak, but not enough to ruin a DD motor.

Clip one shunt will tone it down,, but I never heard of that replace it with some wire deal. Wouldn't that be similar to soldering it, to INCREASE power?

 

[Samd]

That would for sure.
A quick read of the sunwin thread shows that these things are massively overpowered compared to the sticker.


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[e-beach]

Just a thought? Before you get too far along chomping on things it might be a good idea to check your "cheap" power meter ........

YKick makes a very good point. I was taking it at face value. Not the best way to do things.

So, to the point, what kind of ammeter are you using? Got a make and model? How is it hooked up? That is step one. Let us know.

 

[Ianhill]

I agree first protocol make sure your measurements are accurate, I had my gauge reading 400kw when on full load and over 1kw with my two 30w leds so i chased back through the system and had massive resistance on my negative sense lead for the shunt to read the voltage drop once fixed I was getting 3.7kw at 68v which was correct to my math for the controller, still don't nw my phase amps mind you.