ConchZ2

It depends on what your alternator is producing, this is a function of your speed and could be as low as 35 amps, but let's just say you are averaging 70 amps during normal city driving. If your amp is drawing 90 amps at max output, you are already consuming more than is being produced, and that’s not counting what the car might need, i.e. headlights, HVAC etc. The effects of this will be determined by how you use the system and how fast you are driving. When will you crank the system? For how long? How often do you do this? Is the car running when you blast the system? It all boils down to how fast you are driving and how frequently you put your battery into a state of discharge. Anytime you are using more amperage than is being produced by the alternator, you are in a state of discharge. The more charge/discharge cycles you put your battery through, and the severity of the discharge (how far down the battery is drained) can significantly shorten its life span and the life of your alternator.