Is my car's subwoofer causing my electrical probems?

Is my car's subwoofer causing my electrical probems?
Added (1). I have an 02 honda accord with a fairly recent battery. I bought a little 300-500 watt subwoofer that is powered and installed it myself. Within months, the battery had some serious problems. When turning on my lights, the stereo would turn off. Within the next couple of weeks, the car would completely turn off when i turned on my lights or pressed my breaks. I had the battery replaced and everything was fine. The sub isn't hooked up right now.
What would cause this?

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