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Message started by Dave on 04/28/25 at 04:45:03

Title: AGM Battery death.
Post by Dave on 04/28/25 at 04:45:03

Last week I took my F800GT out for the first time this year. The weather was nice, the roads were dry, and I had a few errands to do. The bike started up - I wasn't sure but I thought perhaps the starter was just a bit slower than normal......I wasn't entirely sure as I had my earplugs in and the bike started up almost immediately. I put the bike on a battery tender every few weeks until the charge is complete (I don't like leaving the tender on continuously in case the tender malfunctions).

The first leg was a 20 minute ride to visit a friend in a nursing home. It was nice to be on a bike again - I felt blessed to still be riding while visiting a man who is only 5 years older than me, and knowing that he will never be able to go home again and is just waiting to die while bedridden. (Genetics is not always kind to people).

The bike started right up for my ride home, and I took the back roads to enjoy the ride. I passed a garage that I just recently learned was owned by a friend I had not seen in nearly 30 years. As I passed I saw him sweeping his new garage - so I stopped for a quick reunion visit. We chatted for about 30 minutes as he showed me all his projects.

When I went to leave I turned on the key and the dash lights came on - but when I pushed the start button I got nothing. The dash lights all went out and the electrical system was inactive. We tried charging the battery, jump starting it with his riding mower battery, jump starting it with a Lithium battery jump box and nothing worked. The instrument lights would come on - but pushing the starter button would kill everything. We tried push starting the bike across his long garage floor - but the 12:1 compression ration was more than the traction would allow on his smooth concrete floor and the back wheel just slid across the floor.

I called my wife and she came and got me, I returned home and hooked my trailer up and went and retrieved my motorcycle. When I got home I checked the battery voltage it showed around 12 volts - but when the key was turned on it dropped to 6 volts. Putting the battery on a tender would show it was charging for a while and it would reach sufficient voltage to turn the tender OFF and it would test at 12.5 volts - but as soon as you turned on the key the voltage would drop to something around 6 volts.

I ordered a new Yuasa AGM battery that was identical to the old one. I added the acid and let is sit for a couple of hours to allow the acid to absorb into the glass matt, then put it on a 1.5 amp charger until it was fully charged. I then installed it in the bike and everything was normal again and the bike started right up. I had several error codes to clear for both "under voltage" from the battery failure, and several codes for "over voltage" from my attempts to jump start the bike.

SUMMARY: So my reason for posting this is to let you know how AGM (Absorbed Glass Matt) batteries can fail with little or no warning, and that they also can short out in a way that it is impossible to jump start the bike. When this battery failed it created a short that would take all the current from the jump start device and run it through the damaged battery - and not leave enough current to operate the starter or electric circuit of the motorcycle.......the damaged battery was basically a dead short.

I looked through my files and this battery was purchased in 3/2020 and failed in 4/2025 - it had provided 5 years of service. The original battery was the same AGM type battery and it operated from somewhere in 2016 when the bike was new until 2020 - it had provided 4 years of service (I don't know what kind of care/maintenance it had received from the previous owner).

So it appears that an AGM battery is likely to fail after giving 4 or 5 years of service. Failure of the AGM battery can come with little or no warning - it can operate fine and then fail instantly at the next attempt to start the engine. (I had a similar experience on a Honda ST1100 where the battery worked fine for 2 legs of a ride and then when I stopped for fuel the battery wouldn't even turn on the neutral light. This time the bike could be jump started and I made it home - but even after 40 minutes or riding the battery was still dead when I got home).

I guess that none of this should be a surprise, I believe the batteries in my car are similar and need to be replaced every 4 or 5 years - but they seem to provide some warning by powering the starter slowing than normal. And sometimes the car just won't willingly start in the morning and you know the battery is ready to be replaced.

The big surprise to me is that this battery shorted out internally and it prevented the bike from being jump started so I could make it home. A jump box in the saddlebag would not have started the bike up and allowed me to get home.

So now I need to decide - do I automatically replace my batteries after 5 years of service (or should it be 4 years)? Do I wait until it fails before replacement and hope I am not going to be stranded somewhere when it does fail? I do believe that a 5 year old battery should be replaced prior to going on any long trip!