as soon as i put a system in my car, whenever i would drive at night and the bass would hit the lights would dim. the amp for my system can draw a max of 40amps. to try to solve the problem i was going to install a 1/2 farad cap. i talked to a few people that said it was probably my battery and one of those optima gel cell batteries would cure the problem. so i got the smallest size optima and installed it in the trunk using my previous 4 ga wire and got more to run the ground from the batt to the block. i also have a ground right to the frame from batt. after i did this the same **** was happening so i got the cap. i put the cap in and wired it all together. the cap has a digital read on the top so i can see my voltage. every day ihave to charge that battery because my alternator just doesent turn on when the battery gets low or the lights or system are on. the battery fully charged will read12.75 on the cap by the end of the day i'm at 10.5 or less and when the cap gets below 9 it doesent read anything at all that's about when i have to turn my headlights off just to keep enough power to provide spark. when the car dies it's dead untill i can find a jump. do you think it's the voltage regulator in the alternator, the alternator will turn on every couple of days just not consistantly. thanks, let me know what you might need to know and what you think thanks
-John