So I'm definitely looking at LiPo4 batteries now.  $3500 should get me into 360AH of LiPo battery bank and as these can be drawn down 80% without damaging them that means I can use as much as 288AH of power before worrying about it

That should mean I can set the generator to come on a LOT lower (about 22vdc under load I'm thinking) which means a LOT less genset runtime, less propane as well.

In fact, I'd say it's unlikely I'd need the genset 75% of the year.

The only think I have to consider now, I think, is how to make sure they don't get draw down 100% in the winter and held there for a week (which happened with my GCB's this winter)...however, they have a power shutoff to protect them so I may not have to worry.

I've also got a place to keep them WARM!  Woot!  The back room was originally intended to house batteries until I realized no amount of venting would make me happy.  With the LiPo's they will be in the back room, kept warm and hidden   

I'll have to put the Inverter back there too but should be able to leave the charge controllers where they are for now and run the inverter switch to the porch so I can turn it on upon arrival just like I do today.

This will also give me a LOT more useable space in the porch and solve another issue I had which was dealing with venting which is currently through the wall, when I build the addition.  Now I can make some changes without concern.

The only problem with these is I was just told they only have 3000 to 5000 life cycles but then I was told that is at 'normal usage' lol -- come on folks.  I schooled the salesman.  He then said that was at 100% DoD.

Since I'm running more like 15 to 20% DoD I'd get 20+ years out of them. 

If so I'm doing it.

Chatted with a sales rep on the Big Battery store batts above and he agreed those would do what I needed and then some.  So I may go with the https://bigbattery.com/products/24v-3x-mule-lifepo4-360ah-9kwh/?utm_source=Website&utm_medium=LearnMore&utm_campaign=Analyst&utm_id=ButtonsCamp setup.

I figure it will be a little heavy getting them into the back room and I'll have to do some changes but I'll end up with MORE capacity not less (I know it sounds nuts) and no more watering, worrying lol...just have to make sure they cant be killed but it sounds like they have a cut off to protect them.

I received a reply back on the SimpliFi's and it was the draw each battery can handle vs the AH rating.  So yes, I'd be fine with just one batter as long as I didn't draw more than an inverter capable of around 1500 watts.

24V 3x MULE - LiFePO4 - 360Ah - 9kWh - BigBattery.com
$3400 for this bank of 3 120AH batteries giving 360AH of Capacity of LiPo backup which HAS to be better than 660AH of lead

Thanks guys -- I received an email from a sales rep that said I'd need THREE of those LiPo batteries.  What the??? 

Not much point then.

But he basically said with my battery bank he'd recommend going to 50% of that (so 330AH) and then seemed to have math that said 450AH of LiPo equaled 330AH of Lead....ah...no.

But didn't seem to get that I'd only be using about 40% of the AH cap on the battery when I'm at the cabin nightly (and that's likely spring and fall vs summer when I have a lot more solar production)....at about 40% nightly I can't see why I'd need THREE $2500 batteries.....

What am I missing?  Seems to me ONE of those 24v 150AH batteries should be all I need if I'm only using a max of around 60AH between sundown and sunup....specially when I set my genset to run at 24vdc under load to prevent dropping very far (lol I know, that's probably way higher than most but I don't want to replace batteries lol).

Hi Guy's ! Been some time.  The other problem with Lithium is that you do have recharge them !  When going from an old lead acid that has lost capacity, the extra capacity of being able to go down to 10% Soc with lithium, will take more solar or gen run time.

Not a good thing to find out in Winter Offgrid,  especially if you are not close loop charging the LFP. 
Close loop is where you save the charge time Roger?

Don,  what ever happened to Glen the moderator? Hope you and Karen are Peachy!

Great work! That seems like a difficult location to build in, but the views make it well worth it!

I agree with your assessment of what lithium battery capacity could be used. The greater usable capacity of the lithium means less required total capacity when compared to flooded lead-acid batteries. We use fewer kWh of power on an average day so I believe we can get away with about half that capacity. Now I am torn between going to lithium immediately or working out the present GC-2s for another couple of years.

I will have to move them inside the cabin which will mean relocating the inverter as well and routing new cables from the CC. Doing that will also mean the entire large exterior battery enclosure can be repurposed. So bonus #1.

Bonus #2 comes in the form of lithium recharging faster from the same size PV array as the lithium cells have lower internal resistance. Bonus #3 = no more watering.

Just be sure that the battery can discharge at the rate you need for the length of time you want. That may influence the choice of one battery or two smaller capacity in parallel.

I was doing some simple math and I think this one 86lb battery will provide more usable power and last longer than my GCB's -- like more than twice as long) and I can keep it in the room in the back where it will remain 50F or more year round.

If I moved the inverter back there as well, I have a remote switch I can put in the porch to turn on the power...I'd just have to run the charge controller and cables to the back room.

Might motivate me to put a good door on the back room and finish it too  and give me a LOT more room in my porch as well