After some seconds/minutes on loud volume a lot of distortion and nois

Hi,

my charge 2+ is a little wasted. It doesnt charge very well anymore. Charge status is also shown wrong. Shows full if empty. On little volume it works quite well. But if increasing volume it starts with a lot of distortion/noise and really sounds bad. This problem is more likely if not constantly on charge.

So I think it may be a battery problem?! Not the speakers. Because for a least some seconds it can work on all kind of volume. Do you think I should try put a new battery in it? Or can it be a mainboard problem?

thanks