Dual Battery System - Not enough auxiliary power.

Last night I slept in my car for the first time. Since owning it, it was the first time that it rained and I wanted to make sure that the canopy didn’t leak and get my new bed wet. (It did have some minor leaks but I’ll post about that another day).

I wasn’t ready to sleep but I was cozy in my new bed. I unlinked the two batteries from one another so that the master battery would retain a complete charge and ran a light in the back for a few hours while I pottered about. This morning however, the car struggled to start. Something was clearly amiss.

My first problem was that I had no idea which battery each thing was running from. I assumed probably all the cigarette lighters, driving lights, winch, perhaps the internal lights were running from the auxiliary battery but I needed to check. I unlinked the two batteries again then removed the auxiliary battery from the circuit by disconnecting its terminals then checked what stopped working. It turns out the only thing I could find running off the auxiliary battery was a cigarette lighter plug behind the drivers seat. That isn’t much use to me because I can’t reach it while I’m in the back.

Tomorrow I’m going to have to pull some things off the main circuit and get them running off the second battery. I’ll start with the light in the back and add a switch that I can reach from bed. Then I’ll also rig up the cigarette lighter in there so that I can charge my phone or laptop in there.