Re: Voltage meter
Both of your batteries should be "Marine" batteries. I think you mean Marine Starting and Marine/RV Deep Cycle. Regardless -- how you wire it depends on how the two batteries are wired. If they are wired to a dual battery switch the wire it to the +12 volt and ground terminals on any other gauge. The battery you have selected will be the battery the voltmeter is monitoring and that battery will be the one that is charging. If you have BOTH selected then the meter is monitoring the entire electrical system. If the deep cycle battery is totally isolated from the starting battery, then a simple switch could be used to select which battery you want to check. We really need more details on how your batteries are wired.
