i'm getting very low battery warning on my 335i idrive. i just wanted a headsup on if its ok i\or halfords change the battery. i've read in the manual that some easy settings like radio\time\ memory seats etc may have to b reset. has anyone changed the battery themselves or should i buy one from halfords and get bmw to change as i have it booked in a few weeks from now on a different matter. also the cars 3 years old, is it normal for the battery to go now??