Dear MOby,

My motorcycle is about 4.5 years old, still has its original battery, and lives in an insulated garage. I always connect the battery to a trickle charger/maintainer. When I turn on the electrical system without the motor running, the battery registers 12.3 volts; with the motor running it registers about 14.4 volts at 4000 rpm. I have not had any problem starting the bike. I frequently go on long motorcycle trips, however, and it would be inconvenient to find out I need a new battery while a long way from home.

Should I replace the battery in my motorcycle even though it’s still working well? How do I know when it’s time to change the battery?


John B.

Responsible type, eh? How I wish I were more like you… If your bike’s only 4.5 years new, we’ll assume it’s a newer, sealed type. Yuasa says on its FAQ page:

SEALED AGM BATTERIES (Absorbed Glass Matt) – Last Longer. They are not “open to the air” by way of a vent tube. They do not lose water. They are also packed tighter. Plates do not vibrate causing material to shed from the plates and short out. Or worse yet, simply breaking apart in some high vibration applications. Sealed AGM batteries typically last 3 to 5 years on average. 6 to 8 years is easily obtainable with proper maintenance. Typically sealed AGM batteries will give warning before completely dying. They will start slower, and require more charging. This is your clue to replace the battery. Typically they do not fail all of a sudden. Conventional “acid-filled” batteries have a harder life, for many of the reasons listed above. Conventional batteries typically only last 2 to 3 years on average. Although, 4 to 5 years is possible, in the best environments, and with excellent maintenance.

It also depends where the bike lives: Hot and cold climates are both harder on batteries than temperate climes, and bikes that get ridden regularly are easier on batteries than ones that sit for months – though a good battery tender with a float feature negates much of that. In fact, I was bragging about the Shorai lithium-iron battery in my bike not long ago, which must be seven years old now and has never seen a charger, when my friend Jim said big deal, the original equipment sealed AGM battery in his VFR lasted 9.5 years, and his 21-year old Ducati is only on its second battery. So, sealed batteries can last a long time especially if you’re OCD about maintenance.

According to several sources including, though, your 12.3-volt reading means your battery may be on its way to Nirvana; a fully charged one should read 12.7 volts or above. Since you like to play with your voltmeter, there are instructions to “stress test” your battery at the same page, along with a lot of other battery tidbits that will let you know for certain if it’s time to replace.

Send your moto questions to [email protected]. If we don’t know the answer, we know who does, and if they don’t know we’ll make up something reasonable-sounding. What do you want for free?

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