Voltmeter Acting up. need help!


My name is Marcos and I working on my first EV, the car is pretty much done, but there is only on problem.

I have added a 200V DC digital meter to the dash to monitor my 72V battery bank… the meter works fine when the car is first turned on, but as I press the accelerator and a load is applied to the big DC motor the goes displays some crazy numbers… when I take my foot off the accelerator, the meter goes back to normal.

The meter has 4 wires in the back, 2 of them are a 12V isolated power supply… and the other 2 are for the readings.

They are connected directly, I mean, the wires go from the meter to the battery bank and the 12V battery (power supply)

Is there any way I can correct that??

I have a cheap multi-meter I got from RadioShack, when I connect it, reads fine… but this cheap meter also shows the meter when I accelerate the car as well…

Is there maybe a diode or some other device that I need to connect to this meter to make it work?

Please let me know

This is the meter I am trying to use (not the RadioShack multi-meter one)

Thank you.