Which is right, serial then parallel or parallel then serial

[OfflineAlberta]

While right now, I run exclusively a parallel string, I do want to eventually wire for a 48v system. So my question is when wiring 12V batteries for 48v do you wire the series first 12v+12v+12v+12v=48 then take 4 strings of these 48v strings and wire them in parallel?

Or

Wire 12v+12v+12v+12v in parallel then take 4 of these strings and wire them in series to create 48v.

Is there a difference? Are there Pros and Cons?

I have heard that series connected batteries are harder to balance for charging without sacrificing chickens to the battery overlords. What gets me to the glory of 48v system using 12v batteries without killing my flock?

Thank you to all you brilliant people!

 

[sunshine_eggo]

In the vast majority of cases, series then parallel.

In that case you can actually see how each individual 12V battery is performing and can check and compare voltages. Should you have a problem with one of the strings, you can simply take that string offline and troubleshoot while still operating at reduced capacity, and you'll likely know which 12V is the problem.

Parallel first loses visibility of ALL 12V. If you have a problem and need to troubleshoot, you must take the entire bank down and find the problematic 12V.

While it costs a little extra, a 48V balancer that seeks to keep each 12V at the same voltage goes a long way to keeping them balanced. Need one per string.

 

[OffGridInTheCity]

The challenge with 4 x 12v in series (for 48v) is keeping them balanced. This is why people tend to use '48v batteries' with BMS/balance rather than 4 x 12v in series.

I've read about the victron solution using several "Victron Battery Balancers" - https://www.amazon.com/Victron-BBA000100100-Battery-Balancer/dp/B01DH6B2D2 - hooked up like this

https://www.master-instruments.com.au/products/64806/Battery%20Balancer.html

Here's an example of a cheaper approach....

There are likely other options - maybe someone will share a good solution that worked for them.

Depending on the balance method (and expense), you may want to parallel 1st and then put those in series so you only have 1 string to balance. But this has the cons listed above.

Did you have something in mind to keep string(s) of 4 x 12v batteries in balance?

 

[OfflineAlberta]

Thank you for sharing, this is really helpful!

I guess I would have another question, why do the 12v batteries connected in series fall out of balance? I am thinking it is something similar to parallels strings. First in line for Serial discharges or charges first, this is why I was asking about the idea of Parallel first then serial (This is a guess for me). If one could use the idea of ring connecting the parallel strings which should offer equal charge and discharge for all the parallel strings. However as stated above the first parallel string in the serial string will still be first to charged and or discharged. The parallel first solution would mitigate the imbalance across several batteries vs the first battery in each serial string when connected serial first then parallel.

I guess another question is which is more valuable, reliable (Ok more reliable) charge and discharge using parallel then serial or using serial then parallel so that diagnostics can be run should it need to? Which one is used more often?

Thank you all again for your time to help me understand!