If the unit has been standing for some time it is common for batteries to "self discharge". If this self discharge is extensive it is likely that the batteries reach a chemical state that significantly impairs the ability to accept a trickle charge from the AC adapter. Should this be the case with your Summit there is a simple remedy to revive the battery to a state in which it can accept charge without difficulty. Apply a rigorous hand crank of at least 140 RPM for at least 30 seconds (the longer the better). Because the hand crank delivers a significantly higher charging current than the adapter this will serve to re-condition the battery to a chemical state that will allow it to accept the wall charge without any trouble. Once you have applied the hand crank (remember, the more cranking the better), you can plug your adapter in and charge as normal. This process can be repeated should the symptoms ever arise again (for example, if the radio is left in the closet for extended periods and self discharges again).