Voltmeter Wiring Help

I've searched through all the threads on this site and on the interweb, but could still use some help on the best way to wire in a new dual digital voltmeter like the one pictured below.

I know it is a cheap part, but giving it a try as I'd like to mount a tach in the old spot for the original voltmeter (that wasn't working). I've got a backup ISSPRO 24V unit and all the threads on here to install it if I have any issues.

TechnoWeenie is the only one who I've seen installed the same VM. He tied into the original 24V wire lead from the old VM and ran 12V from the ignition wire. As I understand it, this will give me the 12V reading from the front battery and the 24V combined reading. This sounds good to me, but also wanted to know:

1) What gauge wire should I use?
2) Can I use the negative lead from the old VM wiring too? -OR-
3) Should I just run a shared negative lead to ground somewhere on the frame?

Electrical is my weakest knowledge, so wondering how I should install to get the most accurate reading with this setup.

I appreciate any ideas/help!

I would use a piece of #18 gauge wire for monitoring the 12 volt side. Putting a fuse inline near the 12 volt source is highly recommended.

You can use the same wires from the 24 volt meter. The ground is the same for both sides of the electrical system. The new meter(s) will come on and off with the key since the 24 volt meter has an external relay in the circuit that switches the ground.

I came across this voltmeter myself and was thinking of using it in conjunction with the 24v meter to look at the voltages of the two batteries independently

antennaclimber said:

I would use a piece of #18 gauge wire for monitoring the 12 volt side. Putting a fuse inline near the 12 volt source is highly recommended.

You can use the same wires from the 24 volt meter. The ground is the same for both sides of the electrical system. The new meter(s) will come on and off with the key since the 24 volt meter has an external relay in the circuit that switches the ground.

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Thanks a lot. Exactly what I needed to know.

I did something similar with a red led voltmeter that also had usb charger ports. I didn't think about replacing the original with a small tach, so that is pretty brilliant. Which one did you or are you thinking about using there?