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Batteries in series or series / parrallel ?

Quartersplash

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I have 6 250 watt Solar panels ,6 135 amp hour agm 12vt Batteries that are now hooked in series as 24 vt. system.I want to add 2 of the same batteries for a total of 8 batteries.

My question is: Should I connect all 8 in parallel, Or would it be better to connect in Series / parallel?

I have a victron MultiPlus 3,000 watt, 24 volt, in her charger.
A victron smart solar MPPT charge controller 250 volt 100 amp,
Also a victron 500 amp smart shunt.

Thanks
 
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If you have a 24V inverter then you need a 24V battery bank. You have no choice but to put the 6 batteries in 2S3P. If you add two more then your 8 batteries must be in 2S4P. If you were to put the 8 12V batteries all in series then you would have a 96V battery.
 
I think you want 2S4P.

Please read Wiring Unlimited. Page 16 and so on. It's nice and clear with pictures for easy understanding.

 
They are AGMs.
I don’t think it’s generally advised to add lead acid batteries into an existing bank. The new batteries will charge and discharge at a different rate than the old ones. This can cause premature failure of the bank.
 
The AGMs that I have In the system or less than 1 year old with not much use.I am adding the same exact batteries To my system. Would that be acceptable ?And I guess my Post needs to be edited to Should I hook them up in parallel or in series parallel ?I am still trying to find that out and I am running out of time. Thanks
 
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Since you're running a 24v system you can't really change everything to parallel anyways, just put the 2 new guys in series and add them in parallel to the bank for a 2s4p setup.

i.e., for the maths:

8x 135Ah AGM's @ 12v in parallel = 1080Ah @ 12v / 50% DoD = 540Ah @ 12v and your inverter doesn't turn on.

8x 135Ah AGM's @ 12v in Series/Parallel = 4x 135Ah AGM's @ 24v = 540Ah @ 12v and your inverter runs just fine.
 
Since you're running a 24v system you can't really change everything to parallel anyways, just put the 2 new guys in series and add them in parallel to the bank for a 2s4p setup.

i.e., for the maths:

8x 135Ah AGM's @ 12v in parallel = 1080Ah @ 12v / 50% DoD = 540Ah @ 12v and your inverter doesn't turn on.

8x 135Ah AGM's @ 12v in Series/Parallel = 4x 135Ah AGM's @ 24v = 540Ah @ 12v and your inverter runs just fine.
Thanks redneck. Would you be able to show me a diagram of exactly how to hook the eight in series parallel? I am learning little by little and I thank you for your help!
 
Optimum way to do it is with some bus blocks and arrange like so:

View attachment 93402
fantastic! After hours of trying to find something on YouTube and asking questions on a couple forums, this is the first good answer to my question for a leyman!
One last question to make sure. These batteries are 135 amp hours each and just to make sure is it four times the 135 amp hours is the total amp hours?
Thanks again and God bless!
 
Yes and no. Each bank is going to be 24v @ 135Ah, 4 banks gives you 24v @ 540Ah,

HOWEVER lead acids like FLA, AGM and GEL are only really usable to a 50% depth of discharge (DoD) so that 540Ah is really only 270Ah of usable power before you start damaging the batteries.

Since most systems are based around Watt Hours as the common unit of measurement, that would be 24v * 270Ah = 6480Wh of usable power.
 
8x 135Ah AGM's @ 12v in parallel = 1080Ah @ 12v / 50% DoD = 540Ah @ 12v and your inverter doesn't turn on.

8x 135Ah AGM's @ 12v in Series/Parallel = 4x 135Ah AGM's @ 24v = 540Ah @ 12v and your inverter runs just fine.
The second line should be:

8x 135Ah AGMs @ 12V in series/parallel = 4x 135Ah AGMs @ 24V = 540Ah @ 24V x 50% DoD = 270Ah usable @ 24V and your inverter runs just fine.
 
You want the main negative and positive wires leaving the two bus bars from opposite ends, not the same ends.
please clarify the above for me.
if all negatives are run to a bus block and all positives or run to another bus block, how does that work if you want the connections from opposite ends of the battery bank?
 
please clarify the above for me.
if all negatives are run to a bus block and all positives or run to another bus block, how does that work if you want the connections from opposite ends of the battery bank?
Look at the diagram that @Rednecktek posted. What I'm suggesting is that the main 24V negative wire connected to the bus bar (and going to the rest of the system) should be connected to the left end of the bus bar, not the right end. This helps balance the load even more. If both of the main 24V wires are on the same end of the bus bars then the battery closest to those wires will see ever so slightly less resistance than the other batteries resulting in that battery draining and charging more than the others. Moving one of the two 24V main wires to the other end of the bus bar helps eliminate that slight imbalance.
 
I would use a second pair of bus bars. The main 24V wires from the battery bus bars connect to these "system" bus bars. The inverter goes to the system bus bars. The charge controller goes to the system bus bars. Everything goes to the system bus bars.

The main 24V positive wire between the battery bus bar and the system bus bar needs the main battery fuse and possibly a main battery switch.
The main 24V negative wire between the battery bus bar and the system bus bar is where you would install a shunt for a battery monitor.

You should also fuse each individual parallel battery string. This would go on each positive wire from the battery to the battery bus bar.
 
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I think I understand
There are two bars for charging (+and - ) and two for inverter?
 
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