Don't know if it makes any sense, this is the best I could do.

 

I also managed to connect it to the i2c interface of an arduino, it seems to be working correctly, I can get values for all 4 inputs via the i2c interface and they change consistently when I change inputs on the pcb.
so why the charger doesn't like them? I really shouldn't have binned the old cells....

 

Your circuit doesn't make sense, one op amp is monitoring a 0.7V input across the 12V battery cell, yet the other does not? What is providing the charger voltage??

 

Sorry if I couldn't draw the schematic properly, of course it's just partial and it's just the battery monitor not the charger. Anyway my guess is that one input monitors the tempererature, one should be the 3.3v, one 12v (half battery) and one 24v (full battery)