Hey guys just gonna post this up here in case anyone else has any ideas on doing something like this. This is how I'm doing it.

Last Spring I built up (2) LifePO4 280ahrs each battery's as my original interstate group 29 L/A battery's were not holding their charge very well.
I Purchased my 2019 AF 990 back in May of 2018 so I got 4 years out of them so I can't complain.

Use the camper pretty often in the seasons except for summertime. So heading up into the snow and being from San Diego have little chance of finding that here I wanted to give a little extra protection to my battery's on top of what I already have.

When I built them I layed 3/16" foam board on the bottom of the battery sliding rack and then wrapped the same material on all four sides of the group sets and even made an overlapping lid that strapped down pretty snugly after I connected up all my series/parallel buss and wiring connections so nothing is really exposed to the air.

So what Im going to do is drill a hole in the rear/top of the battery box, mount a small 2" 12vdc brushless fan over the hole and control it with a temp controller that I mounted in my command center switch plate.




The switch to the right is for the 3k inverter when I want to use that. The one on top will turn the controller on/off when in warmer weather.
Gonna pick up my 12vdc from the cabover light circuit as everything in the camper is LED and when the fan will probably run will be at night when all is dark so no worries.

To help circulate warmer air into the under counter space I installed a small 4" vent cover in the back of the cubby next to the sink area. to help transfer the air.




Another little fix I'm doing is for the small fan below the step going into the head.
This is the cover it came with,



This is cover Im changing it to.



At least it will match the brown heater vent covers already here.
Good thing I opened that area up as I discovered that my 12v+ connection was suspect. Whenever I would move the wiring connections around by hand the fan would go on and off. Easy fix as I rewired both the +/- connections, now all is good.
Then I got to thinking about how that fan is actuated as it comes on when the "Heat" mode is selected on the t-stat. So as long as Im using the propane heater all is good.
But what if Im plugged into shore power and want to use a small electric heater there isn't a way to manually turn the fan on without running the gas heater.

Until now.
So I am going to run a separate (same circuit) unstitched hot wire from the t-stat 12v+ wire under the counter area back to the small fan and just mount a small switch for a separate on/off to be used at any time weather the gas heater is on or not. Going to mount the switch under the step next to the vent cover up high so it wont get kicked or damaged.





Ran the wire in the same loom as what's existing. Only issue will be to stub it up from below to the headspace in the wall where all the wiring is presently routed through. Don't think I have to remove the sink to do it so I'll probably try to fish a pull line up or down to pull my wire up. I will get it one way or another.

Will post up a couple more pics when I receive the fan and get that mounted and switch plate mounted back showing temp readings.

 

A man after my own heart. What's a truck camper good for if not modification. Looks like a lot of thought went into this mod and it should make things simpler for you once it's done. Thanks for posting you mod!)

 

Ugh unfortunately I did have to remove the sink to better access the area for trying to get my wiring from below to above inside wall dead space ( Command center switch location ).

Absolutely a no-go as far as following the existing routing up through the wall area as it's tightly packed and bundles are taped together in groups. Thats the way they should be just not good for adding anything after the fact.

So..... I was staring at the countertop wondering how the heck can I get some wiring from point A to B and then it hit me.





The wood trim piece I installed a couple of years ago would be perfect.
Pop the plugs out and then unscrew it from the wall and then notch the backside for a chase way for the wiring to pass through and then just drill a couple of holes in the wall and Im in like flynn.











So with that done and all my wiring pulled through I reattached the trim piece and then routed my wiring to where they needed to go.

My fan showed up today so I mounted that on top of the battery box along the rear and dropped the temp probe inside and siliconed up the opening. Then I started thinking about blowing warmer air inside and figured I better drill a couple of exhaust holes for the air to escape.
Finished my terms on this part and temporarily plugged the switch console into 12vdc power and flipped the switch.
I still have to program my set points in the controller but temperature looks correct. I did adjust the set point so it would come on and it did and the fan spun fine and after a minute or so I could feel some air exhausting through my little holes.





So this part is pretty much complete and I still have left the manual feed for the under the step circuit fan that comes on with the gas heater.
Hooked everything up and flipped the switch and the fan started up but the gas heater fan energized also, so I was back feeding it. So I will just swap out the small SP switch for an on/off/on switch which should take care of that issue.
Of course everything is shut down for the weekend so I will wrap that up next week but I can reinstall the sink and all the drawers and cabinet doors I removed as well as clean up everything as well as finish setting up the parameters of the temp controller.

 

I went a different route with my two 280 Ah LiFePO4 batteries. I put heating pads on the long sides of each battery. This meshes well with how I use my batteries. I don't pull them out of the camper for the winter and I'm in the camper at least once a month doing maintenance tasks, so I need the batteries to be online and ready to go. I've had this setup for two years now and it's working well.

This summer I did add exhaust fans for the battery/MPPT and inverter compartments to deal with the heat generated by the components. I'm still tweaking that as I'm not happy to blow hot air from those compartments back into the trailer. Blowing out of the trailer would work a lot better, but that's going to take some serious changes.

 

Different ways to skin a cat for sure. Heating pads I think wouldn't work for me as my battery's are kinda boxed in with the foam board and not enough room. Being in SD we never have to remove battery's or winterize unless you live up in the mountains then probably might have to. Were a couple miles from the beach so were good.

Got the controller set points dialed in so the fan will come on at 42* and then shut off at 52*. I tested the probe by wrapping a cold pack around it for a simulation and it all worked fine.
Probably wont even turn it on unless it's gonna be freezing or less.

For the under the step fan that was back feeding I didn't go with a different switch like I originally thought but instead just installed a couple of diodes in pos line from the furnace and dropped another one in the new 12v pos for the manual switch and it works fine now so no more back feeding issue.

Gonna wrap up everything manana and drop some mahogany plugs back in the wood where the screws are and then dab a little urethane to blend them in and you wont know I was ever there.