I use about 15 watts per KM. Hard riding.
I ride 18 kms per trip.
I use say 270 watts and charge about 300 watts.
My charger averages 54.5v @ 2 amps close to 110 watts per hour.
So about three hours charging per 20 kms. If I need balance you can add anything up to 2 hours onto this. But I balance within 10 mins of full charge.
Sometimes it's good to leave the charger on for hours after it reads finished. Some times it can take days for the
BMS to get a poorly balanced pack back in balance.