Reducing controller's current

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Firedog   10 W

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Reducing controller's current

Post by Firedog » May 28 2020 12:42am

I built a tandem using a Crystalyte 5303 front hub and 4840 controller running 54V. It has a 3 power level switch, a Clite cruise control and a thumb throttle. Even in low power, it's more than I want and the bike wants to go faster than 20 to 28mph range we like. In high power, it delivers the 40a plus a bit (2400w w full charge). Nice on a big hill, but I think 25 to 30 amps max. would be more suitable.

I know adding solder to the controller's current shunts will fool the controller into providing more amp than rated. How can I fool the controller in to providing less current than rated? It has 2 shunts, cutting one would be too drastic.

Any ideas. Any side effect that I should know.

BTW, I have 2 more 5303/4840 NOS combos, I plan to list for sale in this forum. Wonderful for tandems or if you need a 40mph single.

john61ct   100 GW

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Re: Reducing controller's current

Post by john61ct » May 28 2020 7:38am

The controller should have limiting settings.

A CAv3 can give you that if not.

Or just go to a less powerful motor!

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DogDipstick   10 kW

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Re: Reducing controller's current

Post by DogDipstick » May 28 2020 8:37am

Limit the amps to limit the power. This can be done by modulating the throttle value.

Never use full throttle, is one way. Another is make your full throttle voltage cap out at 3.7v or something, with diodes to drop ( top out high) V.... not the full 5v that the controller expects... but a lower 3.8v full TH value.... if it never gets full TH it never gives full A? Thats the thinking? It will think you demanded 1/2 throttle, not full throttle...

.....or just buy and install a CA3 that can modulate the TH so the A never gets to high. It does it really fast with the control loop and the shunt.

Or cut one of the two shunts, and make it longer ( or thinner), with a piece of copper, or some shunt metal... then resolder it to the board.

One normal length shunt and one longer ( or thinner) than normal shunt will give you less current.
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motomech   1.21 GW

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Re: Reducing controller's current

Post by motomech » May 28 2020 11:51am

You can grind the shunts down w/ a Dremel tool, very crude and you don't really know where you will end up unless you can measure Amps and go in steps.
The one time I tried this, I didn't get all the metal filings cleaned out and some remained under the PBC, which of course, shorted the board.
I use relatively inexpensive Square Wave controllers, so I just bought another one.
I have also cut one of the shunts of of a 30 Amp controller so I could run it on a mini hubbie. One would think the result would be a 15 Amp controller, but in my case, it ended up being more like a 20 Amp-plus controller(I didn't measure it. Not sure why it worked out this way.
Motomech '11 Motobecane Fathom team, frt. mounted, recycled SWX02 from a Jump rental, 14S (52V nom.) Turnigy LiPoly, PSW Power 9-FET 20A controller. Mean Well HLG-320H-54A, Schwalbe Marathon's, 27 to 28 MPH.

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amberwolf   100 GW

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Re: Reducing controller's current

Post by amberwolf » May 28 2020 5:03pm

There is a thread somewhere about modifying the output of a shunt by altering the circuit between the shunt and the MCU, adding a potentiometer or a resistor, to allow controlled adjustment of what the controller *thinks* is happening, without doing uncontrolled mechanical modifications to the shunts themselves. It requires tracing out circuits on the board, and a bit of reverse engineering of that section of the board, but it's much more controlled results than otherwise.

This post by Jeremy Harris has a diagram to start from:

A similar thread, though I haven't read it (just skimmed), so don't know the results ... hp?t=37068

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