Yes - it should only do this when you've got a flat battery. Other signs of a flat battery are obvious distortion in your tone.
This feature on my Thumb 6er has saved my butt twice mid-gig (I was going nuts trying to work out why my output was so soft and was driving my amp much harder than usual).
Rig: Thumb BO-6 / FNA Jazzman 5 / MIA '75 Jazz Reissue -> Ampeg SVP-CL -> DIGAM 2004 -> 2 x Eden 210XST
Stompboxes: EBS Multicomp, Multidrive & BassIQ, Dunlop 105Q
Band: The Grand Scope