11,000' feet up in the Sierras, after a sub-freezing night at a campsite which was only reachable via a 3hr technical drive through Coyote Flats, I experienced this dread.
Luckily, I wasn't alone on this outing. A quick jump from my dad's Tacoma was all it took to get on the rough road back.
But this got me thinking - what if I had been all alone? Worst case, I could always roll start Old Yeller, however the steep trail would have made this option potentially unsafe. The best way to prevent being stranded, as well as add the capability of house electricity, was to add a 2nd battery in parallel.
Components used:
- 200A isolator relay
- 2x 200A fuses w/ 0 AWG wiring
- Marine deep cycle battery w/ battery box
- Voltage gauge
- OEM Toyota ECT switch from 4Runner w/ auto trans
- Adjustable time delay switch
The Set Up:
The two batteries are wired in parallel, with the isolator relay separating them. Both voltage sources are fused. The isolator relay is triggered by +12V from the ignition, thru a manual isolator switch and a time delay switch. The time delay allows ~ 10s for the engine to start before connecting the two batteries, thus preventing the house battery from being cranked every time the engine is started. In an emergency, I would simply connect the two batteries with a jumper cable.
The house battery is strapped down in the rear cargo area on the passenger side. Eventually though, I would like to mount it underneath to free up the cargo space. Quick connect terminals make it easily removable (for example when powering the trolling motor on my boat).
Since I had the battery already (for free), this setup only cost $115 to do. Absolutely worth it for the ability to power my lights, phone charger, radio, on board water, and inverter without worrying about a drained starting battery.
OEM Deck Lamp and ECT Switches
