Apple iphone Bluetooth won't charge?

[Swagfndr]

Is mine broken or is it normal that the iphone headset won't charge on the base unless the phone is there with it? Rarely use the headset and thought I would charge it overnight so I put it on the base without the phone (only have to charge phone everyother day). Tried to use it this morning and it wouldn't even turn on, put it on the base with the phone and it showed on the meter that it had no charge. It is charging now but I am guessing that it will work once charged.