less than ideal battery bank worth the effort?

[Castiron]

I have been wanting to do a solar system for several years and am now in a position to do it. I will do a whole house system, grid tied, with battery backup. I had been contemplating a Nissan leaf battery for back up. But just came across some AGM batteries manuf 2016 Power Safe SBS 190f that were taken out of service last year, 20- 12 v 190ah with a battery rack, all cableing and breakers for ea 48v string, all at basically no cost.
This may be more than I need so I thought I could rotate the strings in service.
Anyway, in reading here the past few days I am seeing that paralel strings are not recommended, but these cost next to nothing, so would it still be worth the effort?
I also may have the opportunity for more when these are no longer working.
I've been working on sizing the system and it will be 11-14kw. My kwh/day usage for four months out of the year is 75-80 and my lowest will get down to 50.
I'm in central fl which shows 5.4 hrs/ day of sun with roof facing south.

Thank you

batteries.jpeg

[Mike90250]

If those AGM's have not been getting charged monthly, I'm concerned that they may be damaged (sulfated) from sitting idle for a year. 2-3 months is OK for AGM, 30 days OK for flooded.

What's it worth to you - cheap batteries today to tide you over for 6 months when they start to fail in the fall and you have to replace before winter ?

With your battery backup, will you have a generator too ?

[Castiron]

I forgot to mention what the batteries are, Power Safe SBS190F. (edited op with this info)
The batteries rack and cable are basically no cost, so was hoping to get a few years out of them, but 6 months would'nt be worth the effort.
When they are new they have a 2yr shelf life and over 10yr life in float service.
No generator.

[SunEagle]

I forgot to mention what the batteries are, Power Safe SBS190F. (edited op with this info)
The batteries rack and cable are basically no cost, so was hoping to get a few years out of them, but 6 months would'nt be worth the effort.
When they are new they have a 2yr shelf life and over 10yr life in float service.
No generator.

Well you might get more than 6 months out of them but if they are 4 year old and haven't been kept on float there is no telling how they will perform under load.

I would invest in some type of generator for both the batteries and as an emergency power supply should the batteries fail and it is cloudy.

[SunEagle]

Besides the used batteries I am a little concerned that you plan a 11 - 14kw system. Is that all for the batteries or is it going to be grid tied with a hybrid inverter?

[Castiron]

Well you might get more than 6 months out of them but if they are 4 year old and haven't been kept on float there is no telling how they will perform under load.

I would invest in some type of generator for both the batteries and as an emergency power supply should the batteries fail and it is cloudy.

I will be grid tied so the only time I would be concerned about the batteries failing would be if the grid was down from a storm. I'm not concerned about having a backup for the backup, I'll just suck it up if that happens.

[Castiron]

Besides the used batteries I am a little concerned that you plan a 11 - 14kw system. Is that all for the batteries or is it going to be grid tied with a hybrid inverter?

I have only lightly researched so far and have come up with 11-14k. My main goal is to be able to eliminate the power bill, potentially selling some back, and the batteries for night and when grid is down, which isn't frequent.

[Ampster]

I am retired and have a hybrid inverter already. My Nissan Leaf batteries are showing their age so I would go for it. The downside is your time but that translates into experience. The upside is you get free power. Sounds like a low risk decision to me.
At the end of the cycle you have a nice battery rack with breakers and interconnects and some experience so when Lithium gets down to $100 per kWhr you will know how much battery capacity your will need in the longer term.