I did a search so please bare with me if I should have found something.
My headlights grow somewhat dimmer whenever I play loud music with a lot of bass or if I use some other electrical source like lower the electric windows. Basically it seems like whenever I use power for something, my headlight dim, not dangerously but definitly noticably when driving at night. Its like my battery can't keep up.
Is this is just a matter of getting a new battery? and if so, what do you recommend as a more reliable/powerful replacement or might this be a different issue?
http://www.volvo850forum.nl/index.php?topic=19493.0
Hier staat een beetje hetzelfde probleem beschreven.