Struggling to understand battery capacity numbers

Q&A and troubleshooting
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1

Hiya,

Have an off grid house system and am just adding two new 25.6v 200ah batteries to the BMS. It’s a 48v system and I now have 6 batteries (3 sets of 2x25.6v 200ah wired together and each into 1 of the ports on my lynx 1000 to create the 48v). I can’t find a solid answer on what I should be detailing in my BMS settings for this.

Should it be:

Battery bank voltage : 48v

Battery bank capacity : 200ah

Number of batteries in parallel : 6

or

Battery bank voltage : 48v

Battery bank capacity : 600ah

Number of batteries in parallel : 3

Or neither of the above and something else entirely?

Any help would be really appreciated!

2

To make 48v from 25v batteries you series them. So 2 in series.

But since you have 6 it is 2 in series 3 in parallel.

Your capacity will remain the same.

Is each 25.4v battery 200Ah?
If so you have 30, 480kwh of battery (6x 25.4v x 200ah)

At 48v it is still 30 480kwh of battery but you have 3 (strings)x 200ah - 600ah of battery. (3x (25.4v x2) x 200ah)

3

Hi,

Thanks very much for your help with this. Ah sorry yeah so 3 parallel sets of 2 in series.

Yeah uh huh, each of the 6 batteries are victron life po4 25.6v 200ah.

Does that then mean on the BMS settings the values should be changed to

Battery bank voltage : 48v

Battery bank capacity : 600ah (or 200ah)

Number of batteries in parallel : 3

Again, much appreciated

4

Correct

1 Like
5

Brilliant, thank you very much!