Tesla Motors Club
While looking at the charging chart here:
Model 3 NEMA Adapters
I see there's quite a difference in charging rate when going from the 5-15 and 5-20 120 volt plugs to any 240 volt plug. You'd think the miles per hour of charge would just double when going from 120 to 240 volts at the same amperage, but I think there is some sort of "electrical overhead" use, where part of the charging power is used to run the BMS and other things, and by the time that is taken care of, a 5-15 or 5-20 doesn't have much power left to actually charge the battery.
5-15 3 mph to 6-15 11 mph, 5-20 4 mph to 6-20 15 mph.
So while it CAN charge at 120 volts, it will take a long time. And in the winter, with some power being used to keep the battery warm, I'd be surprised if a 5-20 did 1-2 mph, if even that much.
Model 3 NEMA Adapters
I see there's quite a difference in charging rate when going from the 5-15 and 5-20 120 volt plugs to any 240 volt plug. You'd think the miles per hour of charge would just double when going from 120 to 240 volts at the same amperage, but I think there is some sort of "electrical overhead" use, where part of the charging power is used to run the BMS and other things, and by the time that is taken care of, a 5-15 or 5-20 doesn't have much power left to actually charge the battery.
5-15 3 mph to 6-15 11 mph, 5-20 4 mph to 6-20 15 mph.
So while it CAN charge at 120 volts, it will take a long time. And in the winter, with some power being used to keep the battery warm, I'd be surprised if a 5-20 did 1-2 mph, if even that much.