I'm looking for a wire (preferably in trunk, but I can route as needed) that is on only when the car is running (not on during ignition). The ACC line goes to 0V during ignition and I want to avoid using that.

I'm using a PAC-200 battery isolator to run a dual battery setup and I'm trying to avoid turning the relay on, then off, then back on again during the ignition sequence (which is what I presume would happen if I use the ACC signal as recommended).

Thanks for any suggestions...

 

Not sure about the wire, but why are you isolating the battery? Do you plan on playing your system with the car off often?

 

I've got an elaborate carPC setup that stays in standby mode and for the first time in 2 yrs, my optima yellow top didn't start with a 11V charge (I have a smart carPC power supply that monitors the battery voltage).

More than the carPC (which auto-cuts-out), I think the 1F capacitor that is hooked into my audio system constantly draws a trickle current, so even after the carPC cuts off, it draws current from the Optima, pulling it down to where it won't crank anymore.

If I jump the car and let it charge for 30 mins - it'd be good for another 18 hrs, but then it'd be discharged too low to crank again.

Now I've got an Odyssey (11 lb) battery in the trunk, which is completely isolated from the front Optima when the ACC signal is off.

Maybe the PAC200 has a capacitor across the coil which prevents rapid switching and my concern is unnecessary...

(everything appears to be working fine now and my Optima does not drop its charge at all - the Odyssey goes down to 11V before the carPC PSU cuts off current, and sometimes it will be 10.5V before it is recharged, but it is a deep cycle battery, so hopefully will survive this abuse)