Revamp my 12v to LFP or not?

[Rednecktek]

So I could use some input on stepping up my cabin's power game. I have 2 separate systems up there now, a 12v system and a 120v system independent system. The 12v bus feeds lights, stove exhaust fan, and the 2 diesel heaters so it's completely separate from the 120v side.

Current 12v config:
4x DC29 Wally World 122Ah FLA batteries
EPEver 30a SCC
2x 205w panels in series

If you look at the picture of my system below, you can see the 12v bank on the bottom shelf taking up a good chunk of it. On the right side is the rackmount size 5Kw 24v battery I built for the 120v system. I also managed to snag a pair of the 24v battery bundles to make a couple more batteries to put up there, but now I've got a physics issue. The new batteries are too wide to sit in the shelf between the 12v bank and the LFP by a couple inches.

Here's the real BIG kicker in all this though, it's below freezing up there for months on end and I'll absolutely NEED to have the 12v bus working in the cold and function unattended. I can't have the 12v system shut off or die because it got too cold.

So I was thinking, if I got a heated battery kit from SunFunKits and built a single battery to replace the entire 12v FLA bank, that would free up space for another LFP battery under the shelf. It would cost me about $1000 between the kit and the cells which is a pretty big chunk of money but it could be my capital funds project for the next trip.

So, in a nutshell, is it worth it to replace the FLA bank with a $1000 battery to make space or would the FLA be the better option because of the cold?

As a side note, enclosing, insulating, and heating the utility room would be a MASSIVE cost in materials and manpower that I don't have any time soon. It's on the To-Do list but I only get a couple weeks a year on average and if it's not something I can do on my own, it's going to be REALLY hard to do, so it's not an option.

 

[MTM98290]

You could build a box to cover all of it. Foil tape to join foam insulation together with some venting. When you leave put the foam box over everything. It shouldn't take too much to heat it if the interior volume is small. Im sure it could be designed so that it folds when not in use if you get creative.

Our inverter and batteries are mounted in a tool box that is meant to go underneath a flatbed on a truck. A 120v 7w reptile heater pad kept it warm in there without issue last winter. We are at 2800' elevation and not too far from your place.

As I write this it is 38°F outside 44° inside the building and 56° inside the box. The toolbox has no insulation and has a 2 inch air inlet on the bottom and 2" air outlet on the top. The reptile heater has not been on since last winter. We use a plug in programmable thermostat to turn it on and off. That is plugged into a wifi outlet for remote control.

If you had some heat source I bet that you could keep it warm enough. That is as long as you have enough to power the heater. If you do add a heated battery, keeping all of your equipment in an insulated box would keep everything closer to optimum tempertures. And it wouldn't cost much.

For more space between is ther any reason you couldn't rotate the big battery 90° to gain more room?

 

[Rednecktek]

The big battery hangs out the back quite a bit and the new battery would be about twice as long front to back, so with the side of the cabin in the way enclosing the back is impossible. My measuring tape says I'll have jjjuuusssttt enough space to slide the tail of the new battery under the cabin out the back of the shelf. Makes it pretty much impossible to enclose everything.

As for cold, it was regularly just getting up to freezing when the sun went down... Brrr!

The internals of the big battery don't allow me to rotate it up on its side without risking things shifting in bad ways. It was a first build, I learned a lot. ?

 

[jberger]

Based on budget and time, I'd keep what you have until you have to replace it.

You could throw those lead acids in a cheap marine cooler or, as has been mentioned, you can build your own out of foam.
A cooler at a yard sale is probably cheaper than the sheet goods and it doesn't take much foam to really keep the temps up. The batteries will give off some heat when charging or discharging so you probably don't need an external heat source. A small aquarium heater would easily keep up given the thermal mass of the batteries.
Just remember that you need to manage the battery fumes and get those outside, so insulate accordingly.