I have somewhat limited real estate for installing gauges in
the dash. I was wondering about the feasability of using one
voltmeter (with a switch) to read the voltage in two
batteries. One is an Optima Deep Cyle, and one is my standard
starter battery. Any reason this wouldn't work, or would
something about the wiring required remove the isolation
between the two bateries? I am using the "silver fridge
relay" setup from www.vanagon.com

Thanks,
Chris