# Motor monitoring with EV display!



## Yabert (Feb 7, 2010)

Hi all

Since few months now, I search a simple and cost effective solution to read the amps draw by my motor and his temperature.
I have saw some 1000A shunt on ebay at 100-120$ with her display, but I will need to buy another module and add another display to read the temperature. In addition, I don't really like their screen and I don't think it's the best choise.

So, I think use the EV display from Dimitri (mini bms, 185$ now) for my battery pack and I would use a second one to read motor amps and motor temperature. I think it can be a good component to do this and his integration will be nice.
http://minibms.mybigcommerce.com/products/EV-Display.html


Well now, do you think it's a good idea? And how I can modified the Ev display board to read temperature inside the motor instead of his surface (I supposed than the board will be close to the motor terminals to catch amp flow).
Do you think they can have some better solution to read amps and temperature of the motor?

Thanks


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## cbliss (Jun 28, 2010)

http://www.westach.com/ has quite a few to choose from.


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## Yabert (Feb 7, 2010)

How I can modified the Ev display board to read temperature inside the motor instead of his surface?
Someone know how?
I'm interest to monitor amps on motor or on controller and temperature from inside of the motor.


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## dimitri (May 16, 2008)

You can't modify EV Display sender board. Temp sensor is thermally coupled with hall effect sensor for best accuracy of current reading.

Its not trivial to measure temperature of DC series motor since stator temperature is much different from commutator temperature and its the commutator that happens to be the hottest component.

In my own EV I epoxied OEM engine coolant temp sensor into the lift hole of my Warp9 and put a 1k trimpot in parallel with the sensor to adjust its resistance range since it will always be cooler than engine was. Since I kept all my OEM ECU wiring intact, my engine temp gauge now shows motor temp. Even if you ripped out your OEM wiring you can still get aftermarket temp gauge and sensor and do something similar, but its still a stator temperature. If you want commutator temperature you need to rig an infrared thermometer with remote display, not sure if such thing even exists.

Even though I would love to sell you 2 EV Displays  I really don't see a point in monitoring motor current if you already monitor battery current. Assuming your controller has programmable limits, who cares what the motor current is. Knowing battery voltage and current you can tell the power, which is basically the motor power minus some losses. EV Display will show you the power quite acurately on the battery side.


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## Yabert (Feb 7, 2010)

dimitri said:


> You can't modify EV Display sender board. Temp sensor is thermally coupled with hall effect sensor for best accuracy of current reading.


Thanks for the info dimitri. It's too bad.



> I really don't see a point in monitoring motor current if you already monitor battery current. Assuming your controller has programmable limits, who cares what the motor current is


I care to know the motor current to confirm that my "cheap" KDHD Kelly controller do his work.....


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## dimitri (May 16, 2008)

Yabert said:


> Thanks for the info dimitri. It's too bad.
> 
> 
> 
> I care to know the motor current to confirm that my "cheap" KDHD Kelly controller do his work.....


You know everything by knowing the power and since power is the same on both sides of the controller ( minus small heat losses, which are easy to estimate ) knowing the power on battery side is the same as knowing the power on the motor side. Motor current and voltage is irrelevant if you know the power, IMHO.


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