...must have...if - ATN Extended Life Battery Pack with MicroUSB Cable

...I must say you need a high capacity battery for an all night vigil. I'm 67 years old and found it to be uncomfrontable and difficult if you had to recalibrate your compass. I'm exploring a more user friendly strap detach. Also....if you find you need the head band...?....go for it. If not.... there are other high capacity batpacks.... solar chargers and cables for $less$ ! Semper Fi! Godspeed!!