I finally completed my dual battery isolator set up using the CTEK D250S. I know it's not the super cool $50 home made set up. I was fortunate enough too have 2 CTEK engineers and an electrical engineer friend walk me through all the steps and complete the portable power supply for approximately $500 including the battery.
My friend engineer Dan located Ford's auxiliary trailer battery charging circuit and spliced 12/3 SO cord into and the CTEK D250S.
He added the SO cord quick connects to make my unit portable. He wired everything at night in the dark using a basic wire cutter and crimper tool with a headlamp mounted to his forehead. He completed the installation in less than 1 hour. He supplied me with all the wire and crimps.
I used the portable battery box for nearly 4 weeks on a van camping road trip to Canada. The only thing that killed the battery was running the portable Fantastic Vent Fan all night and charging my wife's Macbook during the day with a power inverter instead of the 12 volt power adapter. The ARB has a built in cut-off switch that shuts down when the battery reaches about 60%. Unfortunately, the Fantastic Vent Fan and power inverter do not have any cut off built in.
The 12/3 SO cord is really cool stuff as it's flexible and easily stored inside the van. It rolls up like a garden hose. It can take a lot of abuse as it's coated with some strong rubber like material. We used an extra 15 feet so I can take the battery outside of the van useeor move it to different places inside the van.
I know that it has one extra connection. We had only a few hours for the install and this was the most convenient route at 9 PM in the dark. Even though his company sells the stuff on Ebay and Amazon, he bought the cord at Home Depot because it came with the mail and female ends. The quick connect made it simple to move the portable power supply in and out of the van.
I bought the LifeLine 80 amp hour sealed AGM battery because I planned in advance to spend the extra money. My friend told me that the Chinese battery would be good enough. I wanted a US made battery with clean connections, longer warranty, and one that has been tested in the field by real users like us. At the end of the day, it cost about $80 more than an equivalent Asian import.
For charging the battery at home and on the road when stationary, I bought the CTEK 4.3 charger. I heard about CTEK on the Expedition Portal. I contacted the company directly to get more information and they have been very helpful.
This is not an advertisement for CTEK as I have no vested interest with them. With that said, they are very helpful and will go the extra mile with you. It was an easy 12th hour solution as we installed the unit in the dark with a flashlight. Most of the parts were bought with Amazon Prime and delivered the day before the install. I should plan better.
My buddy informed me at 11 PM that I needed new front shocks. I woke up at 5:30 AM, drank a cup of coffee and had the shocks installed my 930 AM. We were on the road to Canada by 3 PM.
