I charged it again for 4 hours, it was charging for 3 hours then was complete and went into maintenance mode for like an hour. Now it's resting at 13. Thanks so much for everyone easing my concerns. My D3400 just arrived and its on charge now.I probably wont have it in the car for another week because I still have to install my amps, build speaker baffles and tweeter spheres, and build the sub enclosure. Would it hurt to charge the D3400(supplemental battery) now, and then again right before I install it just to be on the safe side? This is my first time running dual batteries and I have a slight case of OCD and want to do everything right. Thanks everyone.