What I know:  The 4 little blue lights blink while charging, and fewer lights flash as the charged battery arrives closer to a fully charged state.  Once the fully-charged state arrives, upon   all four blue lights remain unblinking.  

What I know:  The number of lights being representative of a full charge has been an ongoing issue in the reviews of this product at Amazon.  Some have concluded that the lights are faulty and are not representative of the unit's charged status.

What I don't know:       What does it mean when all four lights flash on and off while it is charging?  This happened, I pressed the power button, and it showed two of the four blue lights, suggesting it needed a charge.  Once it charges, it switches back to the four blue lights all flashing.