Why does my aftermarket alpine head unit in my BMW x3 only work when the...

...head-lights are on? i have an alpine ida-x200 installed in an 06 x3 and it only has power when either the parking lights or the head lights are on it will work on autolight at night but not during the day, also i wanted to know if instaling a subwoofer and amp would cause damage to the battery/ void the factory warranty
 
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