CW wrote:

The problem in both cases is going to be the transformer. To handle amps
like that, it is going to be WAY to big to fit in the tool and way to
expensive to be practicle.

For this sort of application you don't need a big linear-type supply.
The motor doesn't really care about noisy power, so it would probably be
possible to fit a switching supply into there.

However, one that can provide almost 40A at 18V isn't going to be common
or cheap.

Chris