The reason LEDs use so little power is because they are just Light Emitting Diodes, meaning current can only flow one direction through them, so polarity is key, when it's running (+) to (-) they light up, most of the time trucks will hyper flash because the LEDs don't have much for resistance as they are forward bias current gates essentially, adding resistors in series gives the circuit the resistance you need for it to operate as if an incandescent bulb is in its place, putting lots of LEDs shouldn't stress the alternator and battery that much itd be minimal