How to measure controller shunt resistance for CA?

Hi,

Well after 3 years of ebiking I've decided to order a Cycle Analyst.

Thing is the controller I'm going to connect it to, I painted and so the value that Paul at em3ev wrote on it is no longer legible.

I did make a note of it 2.5 years ago but it's been lost since then.

So how do you measure the shunt resistance?

Thanks,
Kudos

I've learned printed/quoted shunt values to be significantly innacurate so I always use another amp/power meter to adjust Shunt value. There may be a way to open and measure internal shunts but I haven't read anything about that?

Comparing meters is fairly "linear" so even a smaller current measured through a DVM (under 10A) ultimately delivers a good shunt setting at higher power levels.

Ykick said:

Comparing meters is fairly "linear" so even a smaller current measured through a DVM (under 10A) ultimately delivers a good shunt setting at higher power levels.

Click to expand...

Ditto on this. That's what we did when we installed my CA a few weeks ago. We didn't know what to set it at, either, so used a 10A DVM and measured a smaller current. It works perfectly.

I use a clamp DC meter and fiddle with it until it's right lol..

There are far more accurate ways to do this, but i would need a good video tutorial to show me how it's done... Anyone ?

well.. maybe..

https://www.youtube.com/results?search_query=measure+shunt+resistance

Thanks for the response, I have a DVM, but what do you actually do?

What and where do you measure?

Kudos

I hate not knowing what to do !

Is it just a case of measuring the resistance of the controllers shunt resistor?

If so, where would I find this resistor inside the controller?

I would prefer to not open it up if possible though....

Kudos

exactly what controller do you have ? ( number of fets . )

knowing the model, we know it's " max " current limiting point.. with that you can guesstimate the Rshunt value fairly well with trial and error and a bunch of test rides.

It's the Infineon 9Fet 30A from em3ev.

I just found this on grins site:
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I just got a Direct Plug-in Cycle Analyst, but how do I know the RShunt value of my controller?
Ideally, you will have some other current reference and then you can compare the readings on the CA with the known readings of another amp or amp-hour meter. So if the Cycle Analyst says 27 amps while a reference shows 19 amps, then the CA's RShunt value needs to be increased by 27/19 = 42% higher.

By default it is set to 1.000 mOhm, in which case the correct value for RShunt would be 1.42 mOhm. If you don't have another current reference, then you can get a decent calibration value based on the current limit of the controller. Look at your continuous amperage draw (second screen) while riding low speeds at full throttle. If the CA says 53 amps while your motor controller is limited to 20 amps, then your best guess for RShunt is 53/20 = 2.65 mOhm.

The exact value of RShunt can vary quite a bit from controller to controller even from the same manufacturer and batch. The 6 mosfet Infineon controllers are typically between 5-6 mOhm, the 12 mosfet controllers are more often between 2.5-3.5 mOhm. Crystalyte controllers can range from 1.1 mOhm to about 2.6 mOhm. The eZee controllers are usually between 1.3 - 1.6 mOhm
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So I presume you mean using this method?

Kudos

Do you have another power meter (amp/watt)? Turnigy, watts up? If not, do you have DVM which measures Amps? It's very easy and simple to setup but if you're not into doing it you're gonna have to settle for approximate value.

I've found the note I thought I'd lost !

So, turns out the value is 2.25mOhm for the 9fet Controller.

I also bought a 12Fet 40A controller recently which is marked at exactly 1,00mOhm.

Kudos

this is a fool proof calibration if you have the equipment:
http://endless-sphere.com/forums/viewtopic.php?f=31&t=31548#p457115

if you have an accurate voltmeter then you can use a highly accurate, 1% or even .5% if you can find it, resistor that you would use in series with the shunt resistor. if you get something like a 10 ohm resistor and use a constant voltage source of around 50V then the current through the two resistors would be about 50/(10+.001 ohm) or about 5A so you can measure the voltage across the shunt and determine the shunt resistance value. you need to solder the leads to the base of the shunt and the kelvin leads should be soldered to the base of the shunt also imo.

I rember a few years back, Methods was selling CAs. He said send your controller and he would measure the shunt and set the CA. He also in that thread, how to test the controller. Don't know where to search for it. http://endless-sphere.com/forums/viewtopic.php?f=31&t=31548#p457115
Anybody rember that? I sure miss that guy.

Dan

kudos said:

I've found the note I thought I'd lost !

So, turns out the value is 2.25mOhm for the 9fet Controller.

I also bought a 12Fet 40A controller recently which is marked at exactly 1,00mOhm.

Kudos

Click to expand...

2.09 was on mine same model

I simply put my multimeter with the probe in the 10A max current measuring mode, and put that in line with my battery to measure actual WOT no-load current slowly turning the throttle to WOT to avoid a current spike. Take the multimeter off and swap the probe back right then, so you don't forget and blow the multimeter the next time you measure voltage (like I've done). Then adjust the CA shunt value until the no-load current matches. The last step is to use a permanent market or etch the shunt value on one of the end plates of the controller.

John