It pretty much involves taking a whole bunch of batteries and setting them up in a combination of series and parallel along with resistors such that the voltage potential between the two sides matches the target voltage.

But I do believe that is missing a part of the equation. Voltage is how hard it’s pushing, but there’s also the question of how well can it replace that voltage when a circuit allows a current to flow.

Kinda like pushing something by bracing yourself against a wall vs pushing it by walking behind it. In the first case, you might be able to get it moving but the force will drop off as it moves out of reach, but the latter case will keep the force sustained until you tire.

I think that’s called voltage droop and I don’t know if it’s a significant concern for batteries. It’s based on the chemistry of the battery plus resistance of internal components (and any extra components you use to put it all together).

Though one thing that is a concern is that the voltage also drops as the battery gets low. If the circuit it powers can handle that, great. Otherwise you’ll need extra circuitry to keep the voltage steady, like voltage regulators, and that will come with a higher droop.

Edit: adding berries on series increases voltage. Adding batteries in parallel reduces voltage droop.