I have some modules that I'd previously removed as bad which I'm experimenting with to see if I can revive them by exercising them and charging them at different rates (while clamped, of course). After the latest charge, one of 4 modules is resting at 8.15v, with the other 3 are 6.79 to 6.85v, which suggests the three each have one dead cell (8.15/6 = 1.36, 6.8/5=1.36). Has anybody on here had success bringing a dead cell in this type of module back to life?
No. Once a cell self discharges well below 1.2 volts there is no bringing it back. If an external force, like running out of gas, causes the discharge the modules can be recovered.
I successfully brought some of mine back to life, by exercising them more often when I did them. Time consuming though
The modules are a number of cells in series. There will always be a weakest cell. When a pack goes too low and that cell dies, if the battery continues to operate you may get cell reversal and permanent chemical changes within the cell. There are techniques to revive the cell but they are mostly worthless once it's gotten to that stage. Lots of people, my self included, have tried the "Zap" method of reviving cells on power tool packs. It works, but it's temporary. I know the Prius isn't a tool pack, but the chemistry is the same, as are most of the issues. A cell once gone through death>reverse polarity has difficulty taking a charge (high internal resistance, which increases in all cells that age), won't take much capacity, has a limited current output (high resistance), and a much higher self discharge, part of the consequence of the damage. Chances are it'll simply go dead again very shortly, and work poorly even if it doesn't.
