Mounting Aux battery where rear heater would go...

[Sailing_Faith]

After a few years of putting it off I am finally mounting my Aux battery.
it is going behind the drivers seat where the rear heater would be.

I have measured and it fits behind the panel, so that is good... running a 2ga wire to the Main battery with an solenoid to isolate it.

I want to wire a switch to allow me to manually switch the batteries to charge with the engine running, have an “off” setting, and a manual “on”.

I am trying to avoid running a separate switched wire from the upfitter terminal, I figure there must be a “switched” accessory wire in one of these bundles...

I can’t seem to find it in the diagram, anyone know which wire I might tap into?

Thanks,

[Sailing_Faith]

Oh, and before anyone asks;

Yes, I will install a grommet in the hole the cable passes through...

Yes, the battery is a vented AGM and will have a vent that passes through the floor.

[Rod's Trucks]

I would suggest mounting the relay (solenoid) in the engine compartment.

That keeps the disconnect close to the battery, so that large added cable is not 'live' to the aux battery space at all times.
I tapped into the Upfitter box with a fuse tap ( piggyback fuse ) setup. My cable goes auxiliary batteries for ham radio gear and inverter ( for small Hot Pot, and small microwave, if I do not bring the Honda inverter gen set)
It is setup to ONLY activate when the key is ON. It works very well and is a very clean install.
Rod J

[Sailing_Faith]

Looks good Rod. I am going to have solar with charge controllers feeding both batteries so my relay needs to be on that end... thanks though.

Anyone know a “switched” wire running through there? If not, I’ll just pull one.

[Mmusicman]

I would suggest mounting the relay (solenoid) in the engine compartment.
That keeps the disconnect close to the battery, so that large added cable is not 'live' to the aux battery space at all times.

Well it breaks the connection close to the main battery, but the aux battery line is still "live" too.
Proper fuse or circuit breaker placement is always crucial.
Battery disconnects are preferred at batt sources.
Ultimately, "extra care" should always be a big part of the design and heavy cable installation.

I think the rear heater location is an excellent place... or anywhere close to the back of driver seat.

Other "design" considerations is whether the AUX battery will also serve as a "starting battery" too... or just serve as an isolated AUX battery just for accessories. Wire gauge and solenoid size will be a part of this design.

Not related: I used to run a pair of MAIN batteries (and 1/0 cable) in BOTH the rear corners of my G van back in the 70's... no battery under hood. This was done specifically for performance, handling, and traction purposes.