Series battery

The "reversed battery" will -2 volts from the battery bank overall... I.e., 6 cells, 5 in proper series, 1 reversed, will give you 10 volts (5 cells series) - 2 volt reversed cell = 8 volts overall.

The "reversed cell" will "discharged" when charging the bank. And "charge" when discharging the bank.

Obviously, charging a "full cell" just gasses/overheats (during loading). And during charging, that one cell gets discharged.

-Bill

If all batteries are full, and a discharge starts, the 5 cells discharge from 100% SoC to xx. The one reversed cell, already at 100% SoC, starts charging--Depending on the chemistry (FLA, AGM, Li Ion, etc), usually some damage will occur to that cell as it charges over 100% SoC.

If all batteries were at 50% SoC, then the cells will have headroom to charge/discharge as current flows until some cells hit 0% SoC and other cell(s) hit 100% SoC.

In general, I cannot think of any good reason to do this... And there are lots of initial conditions and boundary limits where damage to cells (or worse as in ruined cell(s), venting, or even fire) will pretty much be guaranteed.

-Bill