How to find out the Shunt Value on a Controller ?

Has anyone one used a regular hobby lipo charger to find out the shunt value on a controller ?
( I found a you tube video from someone who used a iCharger that has a 10 amp Foam Cutting feature , however , none of my DC to DC chargers have this foam cutting feature )
https://www.youtube.com/watch?v=okpFsoHNE7I


How did you measure and calculate a shunt value on a controller ?

There's been a number of posts and threads about this over the years, and there's a document on http://ebikes.ca for it too, IIRC.

https://endless-sphere.com/forums/search.php?keywords=shunt+value&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=shunt+resistance&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search


But basically:

If you have a way to make a known constant current thru a resistance, that you can then measure teh voltage across, you can calculate it's resistance.

Ohms = Volts / Amps

(Rock sees the Eagle over the Indian; R = E / I)

Alternately you can apply a known voltage across the resistance, and measure the current thru it, but generally it's easier to more precisely measure volts than current with most of the devices people have laying around.


You can also figure out the resistance by successive approximations, if you're using the shunt as the source for a measuring device like the Cycle Analyst. If you know what current it *should* be measuring, by comparing with a meter in series with the shunt that you know is correct, then you can set the CA to some arbitrary value, and if it's too high, then lower teh shunt value in setup, if it's too low, raise it. Change first by half the value or twice the value, and as you get closer, use half the change you made before, untl you get it to read the same as the second meter.

I did not see it on ebikes.ca , I did e-mail them a few days ago but they have not gotten back to me yet, I understand they are always busy .

So / means divided by ? in other words Dived the Volts by the amps ? , so if I have 10 amps I would divide the volts by 10 amps ?

It is so much easier in the video where he uses 10 amps, but he does not say at what voltage he has the iCharger set to .

I do not have any shunt lying around , nor any any multimeter that measures current/amps so that is out.

If I could tell one of my DC-DC chargers to charge a 2 or 3 s battery pack which is just a guess on my part for what the Foam Cutting Setting uses , at 10 amps I could use the method he uses in the video . Which is the easiest way I have looked into so far.
Now if could know what voltage and amperage the iCharger's Foam Cutting Setting uses .
Anyone here have a iCharger 106B or 108B charger ?

amberwolf said:

there's a document on http://ebikes.ca


But basically:

If you have a way to make a known constant current thru a resistance, that you can then measure teh voltage across, you can calculate it's resistance.

Ohms = Volts / Amps

(Rock sees the Eagle over the Indian; R = E / I)

Alternately you can apply a known voltage across the resistance, and measure the current thru it, but generally it's easier to more precisely measure volts than current with most of the devices people have laying around.

Click to expand...

If this is for entering in the CA setup, and the controller is wired for a CA, it's quite simple. Run the motor no- load while measuring the current from the battery. The just adjust the shunt resistance on the CA until the CA reported current equals the current measured from the battery.

ScooterMan101 said:

So / means divided by ? in other words Dived the Volts by the amps ? , so if I have 10 amps I would divide the volts by 10 amps ?

Click to expand...

Yes.

It is so much easier in the video where he uses 10 amps, but he does not say at what voltage he has the iCharger set to .

Click to expand...

That's because he wouldn't set the voltage--the iCharger in that mode should be a kind of current source, rather than voltage source, so it generates a voltage across whatever load it's hooked up to while it's pushing 10A (up to whatever it's max voltage output is--past that point it won't be able to push 10A, and the current will drop).

Meaning, if the load has a resistance of 1ohms, then the current of 10A thru that will produce a voltage of 10v.

(Volts = Amps x Ohms, or E = I x R, Eagle sees the Indian next to the Rock)

I do not have any shunt lying around ,

Click to expand...

You have the shunt in your controller that you want to measure, don't you?

nor any any multimeter that measures current/amps so that is out.

Click to expand...

That's easy to fix. Harbor Freight sells a very basic multimeter for a few dollars (sometimes free with a coupon in their ad) that's good enough to do this.

If I could tell one of my DC-DC chargers to charge a 2 or 3 s battery pack which is just a guess on my part for what the Foam Cutting Setting uses , at 10 amps I could use the method he uses in the video .

Click to expand...

It won't be a constant current. It will change as the cells charge. If it changes slowly enough, then if your measurement is quick enough it won't matter.