I do as follows on my wifes 2018 30 kwh ; I run a test charge and get say 52% battery and 6h 20m charging time.
Calculate 380min/48% = 7.2 min for 1%. Need 28% to get to 80% ; 28*7.2= 222 min. But that is too much as the charging slows down at the top ; so I multiplicate by 0.9 = 199.5 min ~...
