Driving stepper motors, the driver board takes between 24 and 42 volts, 3 amps per motor (4 axis board). They recommend a transformer type of power supply (as opposed to "switching"?)

Maybe I can use the center tap to get 30v instead of 60v or is that not how it works?

I'd like to get as close to 40v as possible as the motors seem much more responsive (used LiPos to get 40v, worked great) than at 24v.

3 lead acid batts would be about 42v, but how to maintain a 10-12 amp maintenance charge on them?

Thanks for the ideas.