It's really not necessary to understand all that crap... just to understand how to use the Ohm's Law calculator at steam-engine.org! http://www.steam-engine.org/ohm.html
Let the math geeks amuse themselves with all the tedious minutiae... all you need to be able to do is plug in the proper values in that calculator, and make sure that the field marked "Current (I)" (which is the amperage) does not exceed what your battery will support.
Andria
Hmm... I may have to get myself a mech now.