Odyssey PC680 battey experience
My most recent battery was the Odyssey AGM battery for my 2002 GSA. It lasted 2 years 5 months and now is totally dead as far as I can tell. I live in FL (hot) and sometimes can not ride for perhaps 4 months due to traveling (I remove the fuse to the clock during this time and as far as I know there is no other load on the battery when the ignition is Off but I might be wrong in this). During this time I do not have it on a trickle charger as the bike is parked in a parking lot (covered with a Sunbrella custom made cover which stands up to the elements). I should put it on a charger while not riding but because of the hassle factor to remove the battery I do not and had hoped the battery would last longer. Recently, after standing for 3 months I had to remove the battery and tried to charge it with an auto charger but it did not revive the battery. I took it to the supplier who has chargers with a fixed Votage or Amperage charge rate and they managed to get the voltage up over 13.5V and I had hoped it had revived. I did a ride and now 2 weeks later it is again dead, i.e., 10.5V at rest and 6 V when cranking the starter. Being an engineer I like investigating stuff and I know that my charging regime, or lack thereof, is not good for the battery. Also an AGM battery has different charging rates and voltages thus it requires a specific charger. I'm not sure if the standard BMW alternator is also a good match for the battery charging rate (it needs to be at least 6.4A for optimum design cycle life) , but I have not checked that.
Prior to that I had a BMW Gel battery which lasted maybe 2 years. The Lead acid battery before that lasted as long if not longer.
So for my type of riding it seems the AGM battery is not much better as I have to remove it any case at some point and I might as well do that with a cheaper alternative.
None of these batteries ever let me down while out riding and clearly it's the lack of frequent charging that's the problem. Just be aware of the specific different charging regimes required for different battery types and thus optimise their lifespan.