Originally Posted by tmex
I have a 2005 12GS and a 2006 HP2. Both are hard on batteries. It is not a software upgrade issue or an accessory issue. With the ignition switched off I carefully measured the current drain on the battery by putting an amp meter in series with the battery cables. Both bikes showed an off current drain of about 5 milliamps. The stock battery will lose enough capacity with this current drain to not be able to start the bike after about three weeks time (at normal temperature - less than three weeks at low temperatures). It is an unavoidable fact of life that you need a battery tender if these bikes are not used regularly (every week or so).
My bike must be special then. I have never used a tender on any bike, including my 05 R1200GS, and have left it sit for weeks, while I was out of town on travel, and never had it not start, even in sub-freezing temps. The bike is always parked outside.
While I agree the battery is marginal, I disagree you MUST use a tender on them. That is, unless you leave it parked for months.