What is Series / Parallel / Multi-String Battery banks

Choosing a Configuration is Harder than Choosing our BMS

When choosing your configuration, it is important to consider how the BMS needs to monitor the cells. 

In Series, Parallel or Multi-string, the Batrium BMS can make it happen.

The diagram below shows a battery with all combination having the same capacity of 6 times a single cell.

6S1P        Higher voltage (x6) with current limit of single cell rating   (needs 6 cell monitors)

1S6P        Voltage of single cell but 6 times the current rating A and Ah values (needs 1 cell monitor)

3S2P        Voltage of 3 times cell but double (x2) the current rating A and Ah values (needs 3 cell                           monitors)

2M3S1P  (Confusingly referred to as 3S2P)  voltage of 3 times cell but double (x2) the current                            rating A and Ah values however needs 6 cell monitors.


Each cell or group of cells in series need to be monitored

Cells wired in parallel should all be at the same voltage therefore only 1 monitor is needed

If using parallel banks of cells, these cells are measured separately and hence need extra monitors (Multi-string).

Why Multi-String?

This is a question is asked regularly.... 

It will require more BMS components and hence more expensive

Generally only adopted when the bank of cells have been repurposed from another application. 

Usually they are already assembled into a configuration that cannot be changed and hence this approach is adopted. 

Alternatively when adding more capacity at a later date multi string can be used to increase the battery bank with more cells without adjusting the original pack.

Why Parallel First and Then Put in Series?

A much simpler and cheaper options with less BMS components and follows the sensible KISS principle (Keep It Simple Stupid).

The links between the parallel cells need to be large enough to ensure that there is no voltage differences and rated to handled the full current of the string of cells. 

There are safety risks if your attempting this with only small balancing wires (NOT recommended) as this has consequence that a trained battery technician will understand.

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