So I wanted to use my MTX subs inside for a party I'm having. I have a battery, a battery charger, the wiring kit, and the amp. I connected the battery to the charger and connected the amp to the battery (both positive and negative). However the red protection light came on...I'm not sure what to do now. My plan was to hookup an old head unit I'm not using to my old car speakers and then connect the subs with RCA's. Will this even work? How can I make it work?