I installed the USA sound system in my NW-2 switcher. It seems that the battery is always dead. I can put the engine on the track & charge the unit for 14 plus hours, and I only get 1 to 1 1/2 hours sound time before it shuts down. Any suggestions or hints how to improve this system? Feel like I wasted my money on this unit. ( It does sound good when it does work! )