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martin-t asked

What is the best 12 volt Series/Parallel configuration for 16 LiFePO4 cells: 3.2 V / 160 AH ?

As the title says I have 16 Voltronix LiFePO4 cells; 3.2 V @ 160AH. I'd like to know the best buss bar configuration to use these cells as a 12 volt 640AH "house" system aboard our sailboat. I realize that's a lot of Amp Hours and I could go with half that in reality. (I have these cells left over from a EV sailboat motor project and thought I'd go ahead and use them).

At this point I have built a custom rectangular compression holder for the 16 cells and they are arranged side by side in two rows of 8 cells. 4P4S comes to mind but I am now finding out there are many ways to configure this kind of setup and I'm confused at this point and would like to do it correctly. A buss bar diagram would be best for dyslexic me! Ha!

Before encasing them I paralleled all of them to balance the cells which were in storage for a long time and they now all read 3.022 to 3.023 volts per cell with my 4000 count DVM.

I have a Volteq 6020EX supply and a RevoLectrix PowerLab 8 to bench top charge/discharge cells...

When the battery build is completed, the charging system for these on the boat will be solar charging only with a Victron IP22 30A 12volt charger as manual backup. I already have four flexible SunPower 170A solar panels (mounted over our bimini cover in two custom light aluminum frames I built which saves 50% weight of glass panels), and four separate Victron MPPT 75/15 Smart solar chargers networked with the BMV 712 Smart, (one MPPT for each panel), which at present are charging two tired 5D 12 volt LA batteries (2P). To date I have seen 600 watts from this solar system and it works amazingly well.

Thanks for any help on beginning my build...

Lithium Battery
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1 Answer
Mike Dorsett avatar image
Mike Dorsett answered ·

connect 4 cells in parallel, then connect these in series. This way you only need one BMS.

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or something like that. Take the main connections from opposite corners.

With the excess current available, I think the old rule of keeping current path lengths equal can be thrown out of the window. IF one string of cells provides more than it's share of current during a brief high discharge, it will then recharge from the remaining cells when the current drops. With Lithium cells having a 96% charge efficiency, (dis)charge equalisation no longer matters as much as it did with lead batteries.

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