I wanted to maximize the landline electrical plug idea that Ford includes to heat the Coolant. So instead of just warming up the coolant, I thought it a good idea to also control other things as well.

Just in case it gets colder than a witches teet during the winter months I decided to install a couple things like battery blankets, a battery charger as well as hooking up the coolant heater.

I installed a small (fully automatic) battery charger mounted just in front of the squirrel cage on the passenger side fender adhered with double sided sticky tape. It fit perfectly.
I then installed a custom J box to house a 20° ThermoCube that comes on at 20° and shuts off at 30°.
Both the coolant heater in the engine block and both battery blankets are controlled by this thermostat while the batteries are charged anytime the truck is plugged in and need to be charged. When coupled with a timer, the truck can benefit from warmed batteries and coolant only when it's cold enough to warrant these things to trigger by the thermostat.

I didn't take any pictures of the install but it turned out... well, Great! Everything is in wire loom and each component has it's own custom plug. For example, when a battery needs service, just unplug and the battery comes out with the blanket attached. The battery charger and 20° ThermoCube is the same way, just unplug and replace if necessary.
With everything running I found it was well within acceptable current draw limits of only 10.0 amps. When charging, the battery charger had a meager 0.4amp draw. Once topped off, I have no idea what the draw becomes but hey, I can live with that.

 

Sounds like a good idea, I've been playing with the idea of adding a automatic battery charger/maintainer. How did you set yours up? Is your charger wired to both batteries? Which charger did you go with?

 

This is the charger I used, it's rated at 1.5 amps and fully automatic.
Just connect it to one of the batteries since they're parallel they both get charged.

 

Sweet! Now you're ready for the cold weather with no worries. One plug and walk away is pretty cool also.

(I apparently can't rep anyone anymore )

 

Therein lies the problem... I've never had success with parallel battery charging -- one always gets too much, and it's easy to fry the one closer to the charger. I'd love to see a charger that (somehow) can read both batts health and charge them as they need. Dream on...

I just pull the ground on each and charge them individually...

 

I've never (knowingly) had an issue parallel charging, I have a "smart" charger (lol). It begins to cycle when the charging is almost finished and tickles the batteries up to full charge at the end of the cycle. I can leave it connected for days, the indicator light comes on to show it's charging so I can learn something about the battery's health by watching how long the rest between charge on cycle is. I wonder if it may help (with a standard charger) to connect the + to one battery and the - to the other?

 

That is not a bad idea at all Rusty... As long as all the connections are tight and clean... Or maybe I should just drive the truck more!

Then again, wonder how many folks have noticed the batt closest to the Alt (and closest to the starter) is the first to go??! Two different Ford diesels and 2x sets of batteries (4 each) and that's what my experience has been...

 

I didn't know how well this little charger would perform coupled to two 1000 amp batteries, so I propped the hood to see the red LED that signifies "fully charged" and within the day that little charger did it's job. Also noticed when opening the door (thus powering the running board and cab lighting), the battery charger went back to work and the red LED went dark so I figured it's sufficient to maintain these behemoth batteries that are nearly five years old now.

 

Post pictures of set up.