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Wiring of 4 12 volt batteries for a 24v bank

martinwvogt

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All, I wanted to check in with the forum on best practices for a 24v system wiring. The current drawing below shows my current wiring:

The issue I have is that battery A seems to be undercharged when looking at my SOC readings per cell.

The next picture is a proposed wiring in order to get the batteries more in balance ...

Any thoughts greatly appreciated.
 

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Your proposed is a non started - it looks like all positives are connected together and all negatives together? which gives 4P = 12V.

2 options are 2S2P or 2P2S.
 
Your proposed is a non started - it looks like all positives are connected together and all negatives together? which gives 4P = 12V.

2 options are 2S2P or 2P2S.
Thanks, the recommendation is to connect the batteries in series first, so that would be battery A and B connecting positive and negatives same with C and D and connect B and D and A and D in parallel. Yes, drawing 2 is garbage. Thanks for the catch.
 
forum on best practices for a 24v system wiring.
Screenshot_20250115-215926_Chrome~2.jpg
The series cables need to be equal lengths. The cables connecting the batteries in parallel need equal lengths.

The batteries can become inbalanced, so before connecting in series charge each up to full with a 12v charger. To prevent the batteries going out of balance fit an equiliser/balancer.
Screenshot_20250115-215837_Chrome~2.jpg
The first option is two balance units, with the battery pairs connected as in the first diagram
The second option uses a single balance unit with the mid points connected.
With lithium batteries the first option is preferred.
 
Thanks so much, the current setup follows your drawing. However, I have chargers connected to 2 separate batteries and I'm wondering if this is the problem I'm getting with my SOC readings. Since I have a 24v system I have a total of 3 charger cables which I possibly can consolidate to 2. I will look into the balancer option as well. thanks so much for your response.
 
Any chargers need to be connected to the same point on the batteriy bank as the inverter / load is connected to ensure all batteries receive the same charge current.
Any charging of individual batteries in any bank of batteries will cause imbalances.
 
if you are connected as 2s2p then you need to use 24v chargers connected at the point they join or a bus bar where they join - in the picture below the charger would connec to the bus bars.

You can't use 12v chargers on a series string of batteries and hope to maintain any sort of balance.



1737051727897.png
 
have chargers connected to 2 separate batteries
You cannot do that. If they are 12v chargers. the batteries must be separated from the series configuration . When in series you must use a 24v charger. Some types of 12v charger could be damaged or damage the batteries, if used in a series string.
 
Thanks everyone for their input, we will make sure the charging occurs at a single point of the bank with a 24v charger. If the problem persists I will install a balancer.
 

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