How to correctly wire 12v batteries

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tonygeekzone

18 posts

Geek

#303394 7-Feb-2023 19:01

Hi there, can someone help with the correct way to wire up 8 X 12v batteries, in parallel for perfectly balanced charging, I have 4 X 4 side by side, not 8 in line, I'll be using a inverter and most importantly a battery charger which I want to leave permanently connected, in the attachment/pictures I'm not so sure how join that set of 4 to another set of 4, and then the inverter at one end and the charger at the other end,is this good or does then even matter?
Thanks.

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15221 posts

Uber Geek

Lifetime subscriber

#3033010 7-Feb-2023 19:07

Is that the 'charger' you have and the manufacturer instructions for it?

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tonygeekzone

18 posts

Geek

#3033021 7-Feb-2023 19:27

No that's just in the diagram, I actually haven't decided on the exact model of charger or inverter, these are easily enough to get.

elpenguino

2913 posts

Uber Geek

#3033031 7-Feb-2023 19:42

Ignore that diagram, it's incorrect and will lead to some batteries doing more of the work than others, and then some will die.

I'll see if I can find a better one.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

tonygeekzone

18 posts

Geek

#3033032 7-Feb-2023 19:49

Ok that sounds great, will that be for the 8 like in my top picture.
it's strange I couldn't find anything online that clearly shows how it should be done.

elpenguino

2913 posts

Uber Geek

#3033034 7-Feb-2023 19:50

This should show the important thing you need to know. Once you've chained all the negatives and all the positives, connect the charging inputs at opposite ends of each daisy chain.

Also, if you haven't already, I suggest giving each battery a serial number and a date so you can tell them apart.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

k1w1k1d

1192 posts

Uber Geek

#3033039 7-Feb-2023 20:00

Is there a reason to use 12v?

24v inverters are more efficient than 12v.

What size are your batteries?

tonygeekzone

18 posts

Geek

#3033072 7-Feb-2023 20:33

Once you've chained all the negatives and all the positives, connect the charging inputs at opposite ends of each daisy chain.

Ok so if I "daisy chain" each set of 4 batteries, what's the correct way to join each "daisy chain" together to make a total of 8 batteries working together as one, is it like this diagram illustrating the join at just one end?

tonygeekzone

18 posts

Geek

#3033076 7-Feb-2023 20:45

k1w1k1d:
Is there a reason to use 12v?

24v inverters are more efficient than 12v.

What size are your batteries?

They are just 55Ah, yes I had read that 24v or 48v systems are better in some cases, I haven't actually made a decision, but the battery charger for 24v are a bit more expensive, I noticed that a charger that is rated at 12v 40amp is only 15 or 20amp for 24v, so this would be a lot slower to charge, although I intend to have it permanently connected.

SomeoneSomewhere

1126 posts

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Lifetime subscriber

#3033090 7-Feb-2023 21:16

12V 40A is equivalent to 24V 20A. It is usually best to think in Watts, not amps. Both are 480W.

With 12V 55 amp-hour, your battery bank would be either 12V 440Ah, or 24V 220Ah. In both cases, it would be 5280Wh.

EDIT: I didn't read the last post and missed the battery size...

elpenguino

2913 posts

Uber Geek

#3033099 7-Feb-2023 21:35

tonygeekzone:

Ok so if I "daisy chain" each set of 4 batteries, what's the correct way to join each "daisy chain" together to make a total of 8 batteries working together as one, is it like this diagram illustrating the join at just one end?

Yep, well done, you've got it.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

Bung

5441 posts

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Subscriber

#3033103 7-Feb-2023 21:56

elpenguino:
Ignore that diagram, it's incorrect and will lead to some batteries doing more of the work than others, and then some will die.

I'll see if I can find a better one.

Given that the connecting leads are adequate parallel is parallel. Your diagram compensates for voltage drops that shouldn't exist especially if the batteries are close together.
The OP's diagram is a refinement of that cf https://www.impactbattery.com/blog/post/how-to-charge-marine-and-rv-batteries-in-parallel

From a comment to that article "This entire article, and all the subsequent theory and diagrams are literally addressing a simple issue of poor terminations.

The layout or arrangement in which the author has described at length with diagrams and current measurements, assumes cumulative poor connections - and also, in the “final” diagram of how to “perfectly balance”, the arrangement falls foul to the same problem - depending on how the terminations are made.

Anyhow, the article is highly misleading - particularly the drawings, which do no depict the poor connections at all."

elpenguino

2913 posts

Uber Geek

#3033108 7-Feb-2023 22:11

Bung:
elpenguino:

Ignore that diagram, it's incorrect and will lead to some batteries doing more of the work than others, and then some will die.

I'll see if I can find a better one.

Given that the connecting leads are adequate parallel is parallel. Your diagram compensates for voltage drops that shouldn't exist especially if the batteries are close together.

They shouldn't, but they do.

Batteries are expensive so it's worth taking care of the details.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

Clima

127 posts

Master Geek

Lifetime subscriber

#3033168 7-Feb-2023 23:32

tonygeekzone:
k1w1k1d:

Is there a reason to use 12v?

24v inverters are more efficient than 12v.

What size are your batteries?

They are just 55Ah, yes I had read that 24v or 48v systems are better in some cases, I haven't actually made a decision, but the battery charger for 24v are a bit more expensive, I noticed that a charger that is rated at 12v 40amp is only 15 or 20amp for 24v, so this would be a lot slower to charge, although I intend to have it permanently connected.

No, the charging rate will be the same.

For 8 batteries in parallel (12V) 40A total is 5A each

For 4 banks of 2 batteries (24V) 20A total is 5A per bank -> 5A each

K8Toledo

846 posts

Ultimate Geek

#3033172 8-Feb-2023 00:59

Clima:

tonygeekzone:

They are just 55Ah, yes I had read that 24v or 48v systems are better in some cases, I haven't actually made a decision, but the battery charger for 24v are a bit more expensive, I noticed that a charger that is rated at 12v 40amp is only 15 or 20amp for 24v, so this would be a lot slower to charge, although I intend to have it permanently connected.

No, the charging rate will be the same.

For 8 batteries in parallel (12V) 40A total is 5A each

For 4 banks of 2 batteries (24V) 20A total is 5A per bank -> 5A each

40A/20A is the maximum output of a 480W battery charger, calculated using Ohms Law.

480W /12V = 40A 480W /24 = 20A

I imagine power drawn from the batteries would vary greatly depending on total capacity & discharge state.

tonygeekzone

18 posts

Geek

#3033176 8-Feb-2023 06:29

No, the charging rate will be the same.

For 8 batteries in parallel (12V) 40A total is 5A each

For 4 banks of 2 batteries (24V) 20A total is 5A per bank -> 5A each

Ok good to know, thanks.

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