I'm using lithium battery , with manual charging and manual balancing since early 2000 in the RC Car/Airplane/Drone scope
Yes ... after a battery is fully charged, it tent to lose voltage .. but I have not much experience on partial charge of lithium battery ... so I did not notice if there is any voltage reduction in this specific scope ... also normally I'm charging at between 1C to 0.5C level, my hobby batteries .. while the PHEV with car charger get charged at 0.2C level .. which should not rise much the voltage of the cell
Anyhow ... I agree that numbers are not 100% clear ... but some indication are quite relevant:
After usage my car had: 3.802/3.816v .. so 0.014v difference
On the next day , with car parked and unused: 3.847/3.852 ... so only 0.005v difference
I don't believe this difference happen in natural way ... I bet it has been due to balancing.
Same after charging : from 3.958/3.966 to -> 3.952/3.958 .. so from 0.008 down to 0.002 difference
As well .. nobody report to have unbalanced pack ... even for quite aged pack ... for me the car is always balancing the main battery
And balancing with current technology is always about discharging the high voltage cells
Both PHEVwatchDog and EvBatMon report the "Target Voltage per Cell" , which is looking to me to which voltage each cell need to be "aligned" by balancing
