Since you seem to not use a lot of power I'd just upgrade your batteries. I'm always in there to save money and if you ever did go 48v in the years to come you can always combine your 24v batteries.. but it might never happen since you're using gas heating and not electric heating. That'd really be a system makeover if you needed thousands of watts constantly.
and I think with all the trees it's very smart to have more charge controllers and more arrays than one big one.
I actually did a very sloppy test last night to maybe mimic much colder weathers. It was 30 degrees in my shop (no heat) and 20 something outside and I just laid a bunch of rock wool over a battery with some 20 watt lizard pad and it kept it at 76 degrees all night and even kept turning off since it was reaching max heat setting.. So it was plenty to heat the batteries.
It was also only 4 inches of rock wool
As far as a pad I recommend no, I think the brands are all just random chinese ones.
Here are 2x 20 watt ones, so 40 watts total
https://www.amazon.com/Temperature-Adjustment-Terrarium-Reptiles-Tortoise/dp/B07ZSFTS5Y/ I think that's pretty good price too looking at other ones? I'd recommend it just from the price, they are all pretty much the same. They're basically laminated with plastic and pretty durable other than if you animals try to eat it (batteries won't do that)
As far as that inverter and your amp hour no I think you can connect as much as you want.. I've never heard of a limit like that.
The device draws what it needs and I guess it must have a surge of 7200 watts? because 24 * 300 amps (it's limit is 300 amp) is 7200 watts and it's only a 3000 watt unit so must be talking about surge power?
You would want a 300 amp fuse I guess is where the inverter's rating is at but you can have massive battery banks connected to any size inverter, the inverter will only pull what it needs to power what it is powering and it just has a "max rating"
See attached pics
This system is pretty half complete but you can see I put a lifepower4 battery inside of 4 inches of terribly laid insulation with gaps and cracks of air and the inverter pulls 60 watts all night (some lights in a different room) + 20 watt heater it is currently 38 degrees and it is 78 in the battery box
So the battery is not used much, 60-80 watts. And the heater itself is 20 of those watts and that just heats the battery from underneath it
I think it's a good test since it is not very complete you can expect better results from 4+ inches and a complete box
Here's a more complete write up of my ghetto test:
There has been a few discussions on self heating LFP or using external heaters and it occurred to me I used to have an iguana and used a small pad heater in the tank that actually got very warm and used low watts. So I looked for them on Amazon and they have lots of models big and small and...
diysolarforum.com
Right at lowes you can get some thick rock wool
https://www.lowes.com/pl/Rockwool--...ing-supplies/4294524376?refinement=2290921190
R30 on some of them. mine should be around R12-R13 since it is the 4 inches but it has air leakage so even less
Some of those are in a bulk package of 12+ idk how much money you got, but can always insulate your entire yurt hahaha
These things are extremely safe too for fire. There are other good tests as well
This is my favorite one but it's long and maybe boring to some people
