The portable charger can take either 120VAC or 240VAC at various amperages. The lowest power, and longest charging time woulb be using 120VAC at 15A, which is a regular residential household wall socket. The best case (for the portable charger) is 240VAC at 40A, which represent what you might have for an electric stove or clothes dryer.
From there it's a matter of math. The ESS is 53 KWH, the 120 VAC, 15A is 1800 W.
Diviiding it out, 53000/1800=29.4, or about 30 hours.
The 240 VAC, 40A connection is 9600W, so 53000/9600=5.5 hours.
The home charger is 240VAC at 70A, or 16800W. 53000/16800=3.1 hours.
All of these time will be slightly longer because they don't take into account any loses. The faster charges will have the highest loses, so the 30 hour time will go up minimally, the 3.1 hour charge is at least 3.5, probably more like 4 hours.
All of these are based on a full charge, meaning you've driven the thing as far as it will possibly go. For me, a round trip to work with an errand on the side is about 40 miles, so even on the slow charger that would only take about 5.5 hours to recharge.
Of course, if it's charging at night, while I'm sleeping, then who cares? It won't be very suitable for long trips, where you might need to recharge before reaching your destination, at whatever recharging facility you can find. My longest expected trip is 150 miles, so I'll just need to recharge once I get there, before coming back home.