What happens when Amperes hour (Ah) and voltage regulation go together to the party?
Portable welder with a small hand truck of batteries?

The item you're looking for is a "buck converter". That performs low-loss conversion of a voltage to a lower voltage at higher current. 2.5kW is a bit of a design challenge though.

Note that these can be made efficient for a large stepdown, so you could have 12V or 48V battery stacks and reduce the width of wiring required.