Battery Bank in Parallel

[headsavers]

Have 2 battery banks composed of 8-12 volt 250AH SLA batteries connected series/parallel ( 16-total ). Can I connect the 2 battery banks ( 48-volt 500AH ) in parallel ( 48-volt 1000AH ) total capacity to 1-VFXR3649A Inverter ? Each battery bank is charged thru FlexMax 80 using solar array supplying 110 Volt at 20 Amps each.

[raysun]

Are all the battery monoblocks the same model, and the same age?

[headsavers]

Yes, about 1 year old and are fully charged because I tried to charge 4 connected in series using a flexmax 80 CC from a solar array of 110 volt at 9.95 amps and it went directly to Absorb ( .2 Amps ) meaning won't take anymore charge. This I did to see if the batteries are good or not.

[SandyP]

Have 2 battery banks composed of 8-12 volt 250AH SLA batteries connected series/parallel ( 16-total ). Can I connect the 2 battery banks ( 48-volt 500AH ) in parallel ( 48-volt 1000AH ) total capacity to 1-VFXR3649A Inverter ? Each battery bank is charged thru FlexMax 80 using solar array supplying 110 Volt at 20 Amps each.

Four parallel strings of batteries is not ideal. Make sure all the cabling is good and ALL the interconnectors are of equal length.
The VFXR will operate with the 1000Ah battery bank however the charging using the inverter will not be optimal.
Your solar panel array should give enough current to meet the charging requirements of the battery bank.

[provo]

Four parallel strings of batteries is not ideal. Make sure all the cabling is good and ALL the interconnectors are of equal length.
The VFXR will operate with the 1000Ah battery bank however the charging using the inverter will not be optimal.
Your solar panel array should give enough current to meet the charging requirements of the battery bank.

I'd say it's marginal. 4380W of panels at full rated power would give 91A at 48V. That's a 9% charge rate for a 1000Ah pack, and that's at a power level you'll rarely see. If you just lost (sold?) one string you'd have a pack that would be somewhat easier to keep balanced, and 91A into a 750Ah pack is a 12% charge rate.

Do you really need that much battery?

[headsavers]

This setup is not mine, it was acquired by a friend and I am just helping him check the system so that he can sell the system or the components. I help people install grid tied home solar systems. Thanks for all your suggestions.

Romeo lampa
retired E.E.