About how long does the battery last? On full volume? And like medium volume? Thanks

You need more watts to that speaker

so what do i need for everything?

I do not recommend using a car battery charger while running the amp lr even using it at all. Reason being is they allow a lot ac tobet through, this will ruin your amp. So instead use an atx computer power supply to power the amp and omit the battery. They do not allow any ac through hardly at all and they are high current output.