Why do the power and sync lights dim when the bass hits?

Used it on my ATV numerous times it worked fine til awhile ago I started hearing crackles each bass thump when I pulled over to check it out (while still playing) I noticed the battery low and for some reason it seemed to drain energy from the LED lights? (Blue power light started to dim each time the bass was hitting same goes for when I turned on the sync light to check if it was just a bad LED bulb) what could be causing this (note the speaker wasn’t mine originally a friend gave it to me and it has been working fantastically til just today)