Club car subwoofer

[Mooreprecedent]

Ok I have a 2006 I believe, club car precedent gas. We put a lift and wheels and tires on it. Well we wanted to out a sound system on it. The speakers we installed sounded awful so I decided to throw a subwoofer in the back storage box. I got everything wired up so it works properly there is just one little problem. When sitting still, If the bass hits hard at all, its cuts off then it'll come back on but as soon as it hits hard again it goes off. Now if its running it doesn't cut off at all. What do y'all think I could do to fix this? I put a capicitor on it and it didn't help so I think my next thing is installing a larger battery since there is no where to put a second battery. Any thoughts are accepted thanks