My IMAX can work with 8s.
I started by replacing bad cell for new ones but the IMAX balancing does not work (or work, but insufficiently).
One or two cells quickly reach max voltage and the other remains ~0.2v lower (I was leaving it overnight but in vain).
Discharging is pretty the same but opposite. One cell reach the min voltage at around 0.3-0.5 its original capacity and it's done.
Also I can't solder properly the tabs that were not primed in the factory (usually, when I split two cells one tab remains primed from the balancing wire but the other is not).
I was trying an acid and alumweld flux but no luck. If I manage to prime it a little, the solder come away when I heat it again :/