Yes you will kill the battery. if the battery is in perfect condition and full charged just running the amp on average you have about 30 minutes till the battery is completely dead. now that doesnt include running the head unit any other lights or devices in the car. if everything is running you you may get 20 minutes till the battery is dead and wont be able to start the car. This is a good guess for a new battery if you still have the original battery in the BMW you may get 20 minutes or less. Cars where never designed to run these car stereo systems and by doing so even a small system you are doing serious damage to the battery and alternator whether the car is running or not.
Yes fast discharge and then fast recharge past certain level can buckle the plates in a battery and cause premature failure, warrantys on battery are only for manufacturer defects so you should have the engine running or use a additional power cell designed for audio. (not cheap)
It's bad to annoy your neighbors like that yes.
yes ur car battery will be damge. it will not be suddenly it will damage slowly.
Absolutely it's bad. You will milk all the amperage out of the battery. When ever an aftermarket amplifier is added the company who made it should have told you to replace the alternator with allot more amperage.
Even it you had replaced the alternator it needs to be spinning to feed amperage into *every electrical system in the car!
It is certainly bad to run your battery down below 10 volts. As long as you don't completely drain your battery, you aren't hurting its life a lot.
My car is a 2011 328i BMW. I have 4 Infiniti speakers. An amp that goes 1500 watts and a subwoofer. By bad I mean will my battery die/get damaged.
