I am installing a 2nd battery in a 1998 Express 1500 conversion van. I am using a r and it is recommended to use a turn on lead from a source that has power when the ignition switch is in both the run position AND the start position (true ignition). I would prefer to tap a wire under the hood but a wire under the dash will do. If anyone knows an easy place please chime in.

Here is a pic of the isolator installation. The big red wire at 9 o'clock comes into the isolator from the main battery through a 150A circuit breaker. The big wire (and the smaller red wire) at 3 o'clock goes out to the 2nd battery. The small black wire at 12 o'clock is a ground, and the green wire at 6 o'clock is the turn-on lead needing a true ignition.

I have temporarily tapped into a "regular" ignition wire powered only in the run position, but I would like to tap into a wire that is on (paralleling the batteries) in the start position as well. This will limit the cycling of the isolator and allow me to start the van using both batteries (or just one, if the other is dead).

Hope this makes sense...

 

I answered my own question; I came across this wiring diagram this morning.


Based on that diagram I found a pink wire coming from the fuse box, probed it, and found what I was looking for.

Here is a pic of the tap.

 

I like your pics on this 2nd battery project. One idea I had when researching a second battery was to use a delay relay to energize the isolator relay so that the second battery and isolator relay would be offline during starting.

 

Thank you, John. Using a regular ignition lead as the turn-on would take the second battery offline; like the way most headlights go off while starting a vehicle. If I were doing it over again, I may have used a that senses voltage and doesn't require a turn-on lead. They are a bit more expensive and I am not sure about the reliability of an electronic switch vice a mechanical switch.

Now all I need to do is try to eliminate or at least minimize the nasty hum our inverter is inducing into the sound system. My son does not deserve this van...