I am installing a volt meter using a relay. I am running a dedicated wire from the battery to the volt meter. The relay gets wired as follows:

30 Battery in
87 To volt meter
86 To ground
85 To fuse panel

Which fuse number on the fuse panel should I connect to 85 on the relay

anyone that has key on power. I assume you are wanting to monitor direct battery voltage while running. Most volt gauges don't use a relay though.

So which ones have key power from the ignition switch?

Why do you wand to use a relay to power the volt meter?
Relays are used to switch high current circuits. A volt meter drawn very little current. You could wire it straight into the switched power.

He wants to monitor the battery voltage directly at the battery. This will give the most accurate voltage reading.

You should put an inline fuse near the battery for the wire to the voltmeter. This way if you accidentally short the wire at the voltmeter, the wire won't act as the fuse and melt.

You could use a voltmeter to find out which fuse to plug your relay into. If it has +12V with the key on, and none with the key off, that's the one.

I believe that #8 and #9, among others, qualify.

--DD

Thanks Dave, for the reply.

could you not just use a Hella fused relay in that case...

Yeah, that will give some protection. The fuse should be as close to the battery as possible. Unfused wires become the fuses themselves so the closer the fuse is to the battery the better.