Not so fast, please.
tunnie, you have a second hand bike on an 06 plate do you not?
http://www.ukgser.com/forums/showthread.php?t=204252
The original manufacturer's warranty, which is near enough all embracing, ran out sometime in 2008.
In all probability the bike is now under some sort of insured warranty, which will be subject to assorted Terms, Conditions and Exclusions. Batteries, if indeed yours is on its last legs, may well be classed - like brake pads - as a consumables and excluded.
Read the terms of your warranty and / or contact the dealer who sold you the warranty.
You may end up looking like a complete Turk if you bowl into NOG brandishing "Yes, it's covered" only to discover that the bods who said, "Yes it is" are riding newish bikes, well wthin the manufacturer's warranty.
Of course your warranty
may cover batteries. If so, then at least you will know and be able to perhaps get a new one.
===
Yonkyo, may well have said as much in his post, referring to 'the BMW warranty'. What we have seen though is some punters getting confused between the original manufacturer's warranty (BuMW's) and a subsequent BuMW branded warranty, available after two years. I think, tunnie, you might well be falling into the latter category.