rearrange batteries with relays?

If its been done before and is a mature technique, I just need some keyword to look for it. If its a clever new idea of keeping batteries leveled by parallelling at lower voltages, I'd like to brainstorm on how to do it with mosfets or something more efficient than contactors. Do they make latching contactors that go to zero watts after latching?

They used four motors or a couple split-armature motors, and varied the speed (actually, torque) by connecting the armature windings in different combinations of series and parallel, and also by varying the shunt fields for fine control. There are quite a few combinations available, especially when a submerged submarine barely needs more than "fast" and "slow".

These days most electric motors will use pulse-width modulation or variable-frequency multiphase drives. Certainly much less complicated than switching banks of batteries around, and you can use feedback to make adjustments for dropping battery voltage.

What's the question?

I've never seen an application for this type of device

It looks like speed was controlled by the configuration of the motor windings

" The motor bus can be split for operation of the motors on each side independently of the other sides (BUS TIE OPEN), closed for parallel operation of both motor groups (BUS TIE CLOSED), connected to the battery bus for battery operating of the main motors (BATTERY BUS), and lastly, for series operation of all motors the positive side of one motor bus can be cross-connected to the negative side of the other motor bus, so that by proper closing of the motor contactors, all four motors can be placed in series for slow-speed operation on the battery bus (SLOW).

Either or both batteries are connected to the battery bus by closing their respective contactors which, in turn, are controlled by one operating lever. "

Graham

OK, thanks for the info on how they did it in submarines. Back to the present. 12 batteries seems like a nice number because it has lots of divisors. You can get 12V with all 12 in parallel, 24V with 6 banks of

The question of how many switches you need and how many poles and throws per switch would be a math problem. You could offer it up to a high school teacher or a professor at a local college as something for his students to work on, although an engineering professor might tell you it isn't practical to use batteries that way.

AIUI they use a buck/boost voltage converter these days.