Because the voltage stays the same while the amps grow, parallel batteries last longer. It will still be a 12 volt system if you connect two 12v 50ah batteries in parallel, but because the amps quadruple to 100ah, the batteries will last longer. Charges are spread among the bulbs in a parallel circuit because they are flowing in several directions over multiple paths. As a result, each bulb will have less charge since the charge is travelling in multiple directions, and the lights will shine less brightly. On the other hand, in a series circuit, there is only one channel and only one location for the charge to travel, meaning that all of the charge is directed at a single lightbulb. As a result, the lightbulb will shine more brilliantly since there is no need to spread the energy. The rule of conservation of energy is not broken because of the difference in power; instead, smaller resistance causes bigger current, which results in brighter lights. The energy traveling from the source to the bulbs remains constant. Because higher power means that more energy in a given time goes quicker from the source to the bulb, brighter lights require more power rather than energy. Because the energy traveling from the source to the bulbs remains constant, the rule of conservation of energy is not being broken; rather, there is merely a difference in power as a result of smaller resistance leading to bigger current, which will result in brighter lights. This means that brighter lights require more power rather than energy since higher power enables more energy to go from the source to the bulb more quickly.
Thank you,
Eddie