You're taking current batteries as the benchmark and comparing them to a 747. A 747 takes about 50K gallons of kerosene. Or roughly 150 tonnes; according to wikipedia the maximum takeoff weight for a 747 is around 500 tonnes. That's also a good explanation of why these big planes are being replaced by smaller ones; using that much fuel is stupendously expensive.

The reason why the engines and fuel are in the wings has more to do with the center of gravity. This needs to be where the wings are for the plane to be stable because of the non trivial amounts of fuel that get burned and the weight of the engines. If you'd store this in the back or front of the plane, the plane would get progressively harder to control through the flight.

With batteries, this is a non issue. You can put them wherever as long as the center of gravity is in the right place. It won't shift as you deplete the batteries. But still, the wings are probably going to be a popular place for this.

Comparing with a long haul 747 is of course a bit unfair. It is worth noting that these planes are being replaced by more efficient two engine planes that are lighter and much more efficient. But I agree it will be a while before we see cross Atlantic flights at that scale. But we're talking short haul here; 1-2 hour flights.