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Old 27-03-2018, 06:38   #1
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2series 3parallel OR 3parallel 2 series ??

It sounds odd, doesn't it!?
12 V system, nr.6 6V cart batteries, 3 to port, 3 to starboard, linked across the boat.

2S3P
I can Connect each pair in series, with a +bar and a -bar on each side, and the connection to charger and loads across a diagonal of the bank (cons: I have three wires across the boat, a bit loose, one for each pair)

3P2S
each set of 3 (port/starboard) is wired in parallel, both positive/negative with a copper bar.
2 inner bars (+/-) are wired via say 2 additional wires, to make each battery work evenly.

Is it any better if loads and charger work on the +/- with TWO points of contacts (a single one would make each battery work differently depending on distance from terminal). ?

Is it just about logistics and mechanical set, or am l missing some electrical considerations in preferring one to another?

E.g. In case of default, is any of these two sets any better ?

Thank you
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Old 27-03-2018, 09:27   #2
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Re: 2series 3parallel OR 3parallel 2 series ??

Parallel then series is best.
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Old 27-03-2018, 21:34   #3
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Re: 2series 3parallel OR 3parallel 2 series ??

can you put them all on the same side? shouldn't be too hard to put 6 golf carts in a 54' boat. it'll be much better.

if you have any cross linking, they should all be fused on both sides. turns into a mess.

and if you have 3 on each side. your only real option is parallel the 3 on each side. but then your long cross series jumper is carrying 100% of load current. and will need to be huge.

if you had 4 on one side, and 2 other on other. you could have 12v banks on each side.

for function and safty, the bank should all be in same spot
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Old 28-03-2018, 09:51   #4
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Re: 2series 3parallel OR 3parallel 2 series ??

I have two symmetrical and equal vanes, say 48x56 cm each.


I will use copper bars for both +/- on each set of 3, thus it be 3P2S

Along the bar, l make for 2 points of contact/junction, at 1/3 and 2/3 of length, for the purpose of equal draw from each battery. Wire or bar, I'll see later.

Also as to loads/charger, isn't it better to go not on a terminal of bar, but on its center!?

Thanks for your feedback
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Old 29-03-2018, 23:47   #5
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Re: 2series 3parallel OR 3parallel 2 series ??

you'd have a pos bus bar on one side. and a neg bus bar on the other side. and a jumper that runs from one side to the other.

that would be a pain as now all loads / chargers need to split and run wires to each side of boat (pos and neg)

so you could then run the neg or pos from one side to the other. and put busses on same side. but cables need to be big like 4/0. if you are trying to run a 2000 or 3000w intverter. the 4/0 is too small
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Old 29-03-2018, 23:49   #6
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Re: 2series 3parallel OR 3parallel 2 series ??

Pic attached

Actually as mentioned before. I would also fuse the top jumper at both ends as well. The mrbf fuses are good for this.

note that banks are wired end to end. so current will be even

take everything to / from the bus bars
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Old 30-03-2018, 04:25   #7
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Re: 2series 3parallel OR 3parallel 2 series ??

Quote:
Originally Posted by john61ct View Post
Parallel then series is best.
Your saying there's an electrical difference between parallel then series versus series then parallel?

Say just four 6V batteries for a simpler example.

Parallel each pair to 6V, then series the two 6V pairs to 12V?

That's better than series each pair to 12V, then parallel the two pairs to 12V?

?

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Old 30-03-2018, 07:10   #8
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Re: 2series 3parallel OR 3parallel 2 series ??

Yes, with a minimal difference in that case.

Add more cells more pronounced, e.g. 6s4p will be much worse than 4p6s.

Paralleled batts have inherent balancing problems, best to keep to 2 strings, 3 max.
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Old 30-03-2018, 12:55   #9
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Re: 2series 3parallel OR 3parallel 2 series ??

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Originally Posted by john61ct View Post
Yes, with a minimal difference in that case.

Add more cells more pronounced, e.g. 6s4p will be much worse than 4p6s.

Paralleled batts have inherent balancing problems, best to keep to 2 strings, 3 max.

Interesting. Why is that?

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