Battery Bank in Parallel

Discussion about the OutBack battery rack solutions
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headsavers
Forum Member
Posts: 8
Joined: Thu Jul 02, 2020 9:03 am
My RE system: Aquired

Just helping friend with aquired Outback components:
1- Inverter/Charger VFXR3648A

2-SOLAR CHARGER FLEX mAX 80

16-SLA BATTERY 12 VOLYS, 250AH

12-LG365Q1C-A5 365WATT SOLAR MODULES

Battery Bank in Parallel

Post by headsavers » Wed Jul 08, 2020 5:14 pm

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
Forum Emperor
Posts: 2525
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Battery Bank in Parallel

Post by raysun » Wed Jul 08, 2020 5:18 pm

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

headsavers
Forum Member
Posts: 8
Joined: Thu Jul 02, 2020 9:03 am
My RE system: Aquired

Just helping friend with aquired Outback components:
1- Inverter/Charger VFXR3648A

2-SOLAR CHARGER FLEX mAX 80

16-SLA BATTERY 12 VOLYS, 250AH

12-LG365Q1C-A5 365WATT SOLAR MODULES

Re: Battery Bank in Parallel

Post by headsavers » Wed Jul 08, 2020 6:55 pm

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
Forum Guru
Posts: 410
Joined: Tue Jun 21, 2011 4:44 am
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 660 Ah C100 - 24V System
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Battery Bank in Parallel

Post by SandyP » Wed Jul 08, 2020 7:15 pm

headsavers wrote:
Wed Jul 08, 2020 5:14 pm
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
Forum Guru
Posts: 463
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: Battery Bank in Parallel

Post by provo » Wed Jul 08, 2020 8:06 pm

SandyP wrote:
Wed Jul 08, 2020 7:15 pm

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
Forum Member
Posts: 8
Joined: Thu Jul 02, 2020 9:03 am
My RE system: Aquired

Just helping friend with aquired Outback components:
1- Inverter/Charger VFXR3648A

2-SOLAR CHARGER FLEX mAX 80

16-SLA BATTERY 12 VOLYS, 250AH

12-LG365Q1C-A5 365WATT SOLAR MODULES

Re: Battery Bank in Parallel

Post by headsavers » Thu Jul 09, 2020 10:26 am

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.

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