"Charging rate is non-linear, because as charge increases, the resistance to charge the battery does, too."
The charging is NOT thru a simple limiting resistor as one might think. The charging is basically a current
source. Besides, if charging at 6.6 Kw yields just a 30 minute reduction versus a 3.3 Kw there would be no
utility in using the higher rate charger. Furthermore, why even provide a QC capability which provides a full charge
in about 30-40 minutes if charge time isn't basically inversely related to the charging current.
If L2+ can't be reported correctly for 6.6 Kw correctly, then don't report it.
"1) charging speed reduced at 80%+ especially at 90%+ - charging rates at 3.3 vs 6.0 are identical"
So, that's at the END of the charging period.
"2) charging speed is not quite twice as fast (or half the time) but more like 1.8 times as fast (or 0.55 the time)"
Oh, so it's now it's 1.8. Well that's VERY close to 2X but not what's being reported, i.e. L2 = 5.5 hrs & L2+ = 5.0 hrs
"3) balancing of cells occurs immediately after charging and can add up to an hour (depending on how much balancing the car thinks it needs) at a slow rate that is the same for 3.3 vs 6.0."
Balancing requires basically the same time in both cases.