The RAT feeds the essential busses, AC ESS BUS and DC ESS BUS, though the ESS TR, not the batteries! Batteries are not charged by the emer gen, and they will drain whenever the emer gen is not on.
As DP said, the RAT feeds the Emer Gen, and this gen is no longer supplied when the gear is down. But if you go-around, rest is possible after the gear is up. Just reset the EMER GEN MANUAL ON switch