Small AGM backup for diesel heater start, vs heated Lifepo4.

[HarryN]

Rolls AGMs “S6-275AGM-RE

So @HarryN asked me to post a bit about my Rolls AGM experience. I have purchased 3 sets of; Rolls AGMs “S6-275AGM-RE For a couple of Van builds & also my Off Grid Cabin. I have had great success with these 6v AGMs as a 2 battery bank in series to make up 12vdc @ 250Ah. The systems I use...

diysolarforum.com

@RV8R was kind enough to post some Rolls battery info in the lead acid battery section of the forum.

It has some info in it about the Rolls batteries under cold weather conditions.

 

[MSRConf]

I recall you can get relatively cheap 16v Ultra Capacitors, from many different places, I messed with one a while ago, that cost less than £30, and it would deliver 80 amps for about 10 seconds on a 12V load, they have a wide operating temp range also.

Only issue was that they are parasitic, they drain slowly so if connected all the time to a battery in parallel, they would drain the battery, but you could put it close to the heater bridged across the +ve & -ve, when you energise the heater, but don't start it up, leave it a few mins to charge the Capacitor slowly from your 12v source ?

Just an obscure out the box thought !

 

[pollenface]

i use 18v makita batteries with a 3amp 13.8v buck converter (& makita battery adapter)

The 5ah 18v batteries are 90wh

Great for all kinds of little projects

 

[Dave911]

I run a small Bougerv fridge in my car 24x7.
When it gets really cold, obviously i dont need much cooling in the fridge. So this is a bit different. I use a 12v 100ah generic lifepo4 battery to run it in a plastic battery box.
I have an isolator and low temp charge cutoff thermostat and relay in the box. The box gets fed 12v via 10 gauge wire right from the battery through a 30amp generic auto fuse.
I also feed the box an ignition signal so the thermostat and charge relay are only enabled/powered when the car is running.
Lifepo4 batteries are supposed to be able to operate near or slightly below 0f degrees. I see -20C places. If you keep the battery charged, my battery is inside the car so it gets warm and then charges as i drive, then no issues. The thermostat I used has a NC contact that could also be used to drive a heating pad. Id stick with lifepo4 connected to your trucks charging system. I can post my wiring setup if you'd like to see it. I drew up a wiring schematic.
Those diesel heaters make some noise. Not sure id want to sleep within a few feet of it.
But propane can freeze up at low temps, unless the tank is big enough. So another problem.