Sharp gf 777 vu meter moving when volume half way

[soundboy]

The battery vu meter moves and the light dims when volume is at half
Do I need to be concerned about a shortage of power that may blow something in my unit

 

[bklyn sound]

Is that when you use the battery test switch... If so my lights dim when I have the box volume up and I use the test switch on Ac power

 

[soundboy]

Yep thanks for feed back