Parallel Connecting VRLA AGM batteries

[Bendesa1962]

Hi everybody,

I have a question about connecting batteries in parallel. I've read articles about connecting battery strings (Who are connected in series) in parallel. It would be wise to use not more then 3 strings in parallel. Otherwise the change would be to big differences will exist between the 3 battery strings and that would effect the total performance of a battery bank.



I have a situation where someone runs a battery bank operational voltage 12V and the battery bank looks as follows

12V 250Ah 4 x connected in parallel. So total storage would be 12 x 250 x 4 = 12000Wh

Would it be ok to replace this battery bank with 5 brand new 12V 200Ah batteries?

12V 200Ah 5 x connected in parallel Sp total storage would be 12 x 200 x 5 = 12000Wh


Both battery banks don't meet the regulation I read about not more then 3 strings in parallel. Although in this case we are actually not talking about real strings because each string just exists out of 1 battery


Many thanks for your contribution

Regards

Johan

[sensij]

So, why is the 4 x 250 Ah bank being replaced? How long had it been in service?

Around here, 5 x 200 Ah x 12 V AGM batteries would cost something around $2000-$2800, depending on quality.

If you can live with less capacity, for around $2500 you could go with something like the Concorde PVX-9150T, 2 V, so 6 in series gets you 915 Ah, or about 11 kWh.

[Mike90250]

I will never endorse parallel AGM banks. They have such low internal resistance, that they don't "share" loads well, the "Best" battery hogs all the load, and quickly degrades, then over and over again, walking the total bank capacity down rather quickly.

[SunEagle]

I will never endorse parallel AGM banks. They have such low internal resistance, that they don't "share" loads well, the "Best" battery hogs all the load, and quickly degrades, then over and over again, walking the total bank capacity down rather quickly.

I can vouch for that.

My 4 x 12v 50Ah AGM paralleled wired system is not what it was when I first built it a couple of years ago. One or two of those batteries are definitely not doing their part of keeping the system properly charged.

My plans are to replace those 4 expensive 12v 50Ah AGM with 2 x 6v 232Ah FLA batteries for less money and IMO a better system because it delivers more power and is not wired in parallel.

Theoretical or not wiring batteries in parallel is a short cut to spending more money.

[bcroe]

My 4 x 12v 50Ah AGM paralleled wired system is not what it was when I first built it a couple of years ago. One or two of those batteries are definitely not doing their part of keeping the system properly charged.

My plans are to replace those 4 expensive 12v 50Ah AGM with 2 x 6v 232Ah FLA batteries for less money and IMO a better system because it delivers more power and is not wired in parallel.

Perhaps the AGM could be wired in series, 48V. Then buck convert down to 12v loads as needed. Bruce Roe

[SunEagle]

Perhaps the AGM could be wired in series, 48V. Then buck convert down to 12v loads as needed. Bruce Roe

I agree that if I was building a much bigger system I would go with one rated at 48volts. When I built this system I was working toward having the 80 & 90watt panels easily moved and used for my RV. The 200Ah 12v battery system was built around the panel wattage but I stupidly went with parallel wiring instead of listening to the experts here and go with a series wired system.

I will chalk up this battery system as my learning one. Live an learn.