If the system is disconnected from AC power and unused for 14 days or more, the system enters a protection mode to preserve battery power. Plug your system into AC power to reactivate it
Applies to:
My system will not work on battery power. What could be wrong?
make sure the battery is fully charged. charge time is up to 10 hours in play mode or in standby. to determine the remaining battery charge level, press and hold the off button on the remote and observe the led on the front of the system
Red: 20% or less
Yellow: 20% – 70%
Green: 70% or more
Off

Try charging the battery on a different AC plug. There may be a problem with the power outlet you’re using
Should I fully discharge my battery before I recharge it?
The Bose® SoundDock™ Portable system uses a rechargeable Lithium-ion battery. This battery technology prefers to be "topped off" rather than a full discharge every time, so you can charge it whenever it's convenient. Make sure you charge the battery before leaving it in storage for any extended period of time