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Small Cabin Forum / Off-Grid Living / Help me choose LFP battery
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# Posted: 21 Feb 2021 16:19

There is another factor that does not work in cost.

LFP can take a bigger charge in general and will charge faster than FLA variants.

I can deplete my LFP bank to 0%SOC, hit the genset and push 100A charge at my LFP Bank, in 4 hours run time I have enough charge to run for 4 days.

If I drop my FLA bank to 50% and push 80A for 4 hours I can squeeze 2 days at best out of them. They will not take 100A, even 80 is on the edge.

LFP costs can vary a LOT. If buying Retail Product like SimpliPhi, BatterBorn or so you are paying a big premium. If you build DIY it can be cheap with Grade-B cells or premium with Matched & Binned Grade-A cells. Even using Matched Grade-A's it's still cheaper than "retail" but they are DIY which is not for everyone.

An article worthy of a good read. ge-market

# Posted: 22 Feb 2021 10:32


One other thing to consider, (which is also making me lean towards replacing my GC2's with LFP) is if there's a chance that anyone else will ever be using your place without you there...

One person unfamiliar with off-grid power can toast your lead acid batteries (FLA or AGM) in one weekend. At least with LFP, if they drain it until it shuts off, it won't kill it (may lose a few charge cycles off the lifetime, but not the end of the world)

We had this concern happen when my in-laws stayed a few days longer after we left. My father-in-law forgot to shut off my inverter. Fortunately, it was summer time and I came back up the following weekend so SOC was still fine

# Posted: 22 Feb 2021 11:08

I understand that Jeff! When we first looked at the place in late Aug 2019 the system with the 4x130ish ah agm's was dated and tired. I was able to sort it out enough to mostly understand what all the bits were (thanx to the 'net) and realized by mid-Nov that I really needed to to something to try to save what was left of the bank before winter set in (even tho we didnt yet own it the seller had allowed us somewhat of a 'caretaker' status while the paperwork issues got resolved {estate thing}). My wife couldnt understand at all why I was messing about with the solar so much and my explanations were, um..., unappreciated.
My advantage was a past mechanic's life but most people I talk solar with get that deer in the headlights expression quickly . You are so right, most dont know what to 'do' with this stuff. And for those same reasons is why I didnt let others use/borrow/rent our rv (sans solar) either.
My wife wouldnt have any idea how to manage what I have rebuilt this all into, she'd be glad to just light up the kero lamps. The batteries would just sit idling along on the scc unused and fully charged at least.
Guess I should really make up a little booklet of 'Cabin Management' as a cheat-sheet ref for her; all those things I just do with the various systems Ive now put in place.

# Posted: 22 Feb 2021 13:19

Quoting: gcrank1
Guess I should really make up a little booklet of 'Cabin Management' as a cheat-sheet ref for her

Exactly what I have done. I have a document I made with photos illustrating all the finer points; anything that is different from what is found in a normal city home. It lists and shows where the shutoffs for everything are and how things work, or must be operated.

Easy enough to do with Word, LibreOffice, your phone camera, etc. Chapters on the solar, water and all for the home, one for the cabin, another for the RV, and other stuff I have. I figure it is the least I can do to help those I leave behind.

At the cabin and in the RV I have a list of "Must-Do Before Leaving" posted right by the door. I figure it helps me too. Of course, those are of no use if nobody reads them.

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