80kWh battery is 80,000Wh; 1W=(1V)(1A), 80,000W=(120V)(666.67A), now if you want to charge that in 20 minutes that’s 1/3 of an hour, you need 3x the current so it becomes 2000A for 20 minutes at 120V, or you could use a 240V outlet and use that 1000A rated extension cord. Oh wait, 4/0 conductors are only rated for…