Backup power scenario

I thinking of using my new LifePO4 battery bank as backup power only, with solar panels on a cart I keep in garage and only roll out as needed. I am charging each new battery now one at a time.
I'll set it all up and test with inverter & solar panel charging and then I could just save all those cycles by leaving it unused.
Q1: Does this scenario make sense or do you have a better solution?
Q2: Can I later leave the bank connected together for AC charging or battery tender?

These are JITa 12.8V 100ah LifePO4batteries.

Thanks!

Lot of money to leave sitting around not using. How much solar do you have?

What inverter do you have? Guessing you can't hook it up to potentially back feed the grid?

You could run a constant load off it like a frig but you would have to watch it for low/high voltage. Do you have a BMS?

Saving the battery cycles for down the road? Hmmm, wonder if later they will be so cheap it wont really matter?

Good Luck....

newbostonconst said:

Lot of money to leave sitting around not using. How much solar do you have? This will be 400ah and I haven't decided on inverter yet because i haven't decided whether to parallel the batteries at 12volt or go 24 volt or 48 volt.

What inverter do you have? Guessing you can't hook it up to potentially back feed the grid? No, I don't want anything to do with the grid or code enforcement

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newbostonconst said:

I was going to check into permit but, if it's not permanently connected, I consider it a temporary, experimental setup.

You could run a constant load off it like a frig but you would have to watch it for low/high voltage. Do you have a BMS? I believe each battery has a built-in BMS. they are Jita Model 003

Saving the battery cycles for down the road? Hmmm, wonder if later they will be so cheap it wont really matter?

Good Luck....

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Well, what you're looking to do is build your own "Solar Generator" and you can peruse the Show & Tell section to see what other people have done. It's not an uncommon thing and makes a great starter project so your first dive isn't a 12Kw split-phase-all-Victron-2-acres-of-panels-ZOMGHUGE-$RealMoney project.

KellyDood said:

Q2: Can I later leave the bank connected together for AC charging or battery tender?

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As long as you got a battery tender for the right voltage. A 12v car charger isn't going to do much for a 48v bank.

As for the voltage, your battery choice will really depend mostly on how much load you want to provide. As a general Rule-Of-Thumb you want to stick with about 200a to the inverter, or 2Kw-ish for a 12v, 5Kw-ish for 24v and so on. Finding room for 2 or 4 batteries on a cart to get your voltage up really needs to be worth it when you go to actually move the thing.

Remember that your Volts add in series, but Ah doesn't. So your 2 100Ah 12v batteries will either be in parallel for 12v @ 200Ah, OR in series for 24v @ 100Ah. Same watt hours, but you only get to add 1 or the other at a time. The Ah will give you run time at load, voltage will let you save hassle & money on wires and fuses.

Make sure you use a good fuse! Fuses are cheaper than fires!

No, I don't want anything to do with the grid or code enforcement

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Don't blame ya!

Oh, the batteries are gonna stay in the dining room with a board for controller etc. - only the solar panels will be on mobile cart to be hidden. I'll have quick disconnect outside with solar connector in weatherproof box.

KellyDood said:

Oh, the batteries are gonna stay in the dining room with a board for controller etc. - only the solar panels will be on mobile cart to be hidden. I'll have quick disconnect outside with solar connector in weatherproof box.

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Aaahhh, that makes more sense. Time to whip out the measuring tape and figure out where to stick 'em.

Whatever you decide on would be good to set it up and run it for a few months to get it working before you need it.

I have about the same size solar generator now, but took about four months to get it setup with the right sized batteries, combiner, and panels for the unattended crockpot cooking I wanted to do. I am using about once or twice a week.

I save about 15 cents on electricity each time I use it, so it’s a bit of a hobby.

Thanks, Chris. I just assembled the harbor freight wagon I'm using as base for the panel cart.

Ever build a sailboat in your cellar? (I can always knock out a wall) The theory was 3 panels on this cart but it looks like maybe (2) 200-watt panels on 2 carts would be much less unwieldy for only a few hundred dollars more plus hardware.

I abandoned the multi-panel cart idea as too unwieldy and am now making individual frames transportable by hand truck for flexibility.
Here is the solar generator as of today

Nice

KellyDood said:

I abandoned the multi-panel cart idea as too unwieldy and am now making individual frames transportable by hand truck for flexibility.
Here is the solar generator as of today

View attachment 88421
View attachment 88420

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Nice

How is the Reliability of your system? Giandel?

It's on standby for power failure - batteries test good.