I have two Westco AGM's currently in service on SPII and 98EV. Regina has a smaller Odyssey because we had to move her 98EV CPU into the battery compartment in order to lower the seat. I get many years of reliable service out of these. Original 98EV batteries lasted perhaps three years. AGM replacements push ten years.
But, you specifically asked about 'downside'. Perhaps there is one. When a flooded cell battery gets old, typically it weakens and shows you some symptoms to prepare for replacement. Perhaps slow cranking. Perhaps failing to start and requiring a jump. Etc. In my experience, AGM batteries work perfectly fine right up to the instant that they no longer work. I've experienced two such failures on other non-Guzzi applications. Start fine and drive off for an errand. Come out of the store and zip, zero, nada. Hook up a jump source and it starts and runs fine until you disconnect the jump source and then dead.
To be sure, it is a rare occurrence. I wouldn't use that one issue as an evaluation point. The advantages of an AGM are just so many in comparison to this fault. Just realize that if and when it fails, you are done. There is not limping home or to a repair facility.
Patrick Hayes
Fremont CA
