I used the Dirty Parts tray, but I didn't buy their kit because I didn't really like the components that were used.

I just designed built my own that was a lot more feature rich and more robust than the " Cheap-Dual-Bat Setup ".

This including a bunch of features that some logic based hardware that also protects the starter battery from a fault like an under voltage condition on the house side.

I am just going to copy paste this from another thread I made a post on, but this should give you an idea of how I went about it...

The most challenging part of the kit was probably just making the cables and actually finding a place to mount stuff. It wasn't difficult but it was a bit time consuming it make it nice.

I made everything myself, including the mains cables which were crimped and protected with adhesive lined shrink + a layer of regular stuff.

My electrical project and needs started with a requirement for more storage/amp hours to run smaller but more persistent accessories loads like an ARB fridge, accessory charging, and radio communications gear... while maintaining saftey for vehical starting for those off-grid adventures and leisure camping trips.

Dirty Parts Dual Battery Tray
2nd Battery
MEGA fusing for mains cable, no crappy car audio stuff here. Crimped and bolted cable.
New Wiring / Refresh crimped Connectors for everything.
Blue Sea ACR (Automatic Charging Relay)
Blue Sea m-LVD(programmable low voltage disconnect feeding both aux fuse panels)
Blue Sea Fuse Panel x 2 (One under hood, one in cab)
Wire
Solar Panel (for emergency or extended stays when I dont feel like starting or driving to charge)
MPPT Solar Charge Controller
Anderson Powerpole quick disconnects for accessories.

As my needs change and as I keep adding items I will eventually need to upgrade my alternator, but as of now, my loads are still well within a safe operating range.

The system is robust and worry free, you can't mess it up even if you tried. Not having to worry about the starter battery going dead is a pretty big piece-of-mind item for me... almost mission critical considering the type of camping I do sometimes... The system is 100% isolated when the engine is not running plus I have protections in place to maintain the health of the accessory battery.

I also take the time to turn everything on to test and measure all electrical loads... Lighting, compressors, ARB fridge, 2 x Ham Radios...




external battery pack made from 3 x old APC SLA cells








fusing, switches, led indicator, and control wiring...





Outdoor = Inside freezer / Inside = Car cabin temp