It is a new year!!, hope everyone had a blast in new years eve!

, I know I did.
Anyway, I've having issues with my M3 Battery since last August. The battery does not hold charge for repeated startups, and I have to recharge it every other week so my car does not put me on foot patrol at work

...
I bought a battery charger , " advanced battery charging system", but after 2 weeks we are back to square one...
anyone having the same issues, please advise...
How often should M3 change batteries anyway