Phil Jones big head LED power light

[RJB280]

Have just purchased a Phil Jones big head, can anyone out there clear up a  little problem for me.?  When I plug the unit into mains  power, should the little green LED that's marked 'power ' light up ?   

Hoping someone can help, thanks

 

[pineweasel]

If the unit is turned off, the green light will be on if it’s charging the battery, but go off once the battery is fully charged. 
 

When the Big Head is on, if connected the power the green light stays on. 

[RJB280]

Thanks for the info that's really helpful, when my unit is plugged into the mains via the USB the green light will not illuminate. I'm assuming there must be a fault with it then ?