Shelf Life of AGM Battery - storage


New member
I just happened to have Odyssey battery leftover - about 2 years old. Never used, or maybe 1-3 cycles.
Every couple of months, I dump the trickle charger on it (ctek) just to make sure it's topped.
Right now, for the past 18-20 months, it's literally been just sitting around.

Was just wondering, what is the ~shelf life~ of said battery in storage/


Provided you are using an AGM charger, you can expect a 2-4% loss in capacity per year even if not used. It is critical that the charger goes through the AGM steps of charge and not just a trickle charger.

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New member
Would it be good practice to put a load on the battery at least 1X a year and then charge it, just to get the electrons flowing....


Expedition Leader
  • Guaranteed longer service life
    With an 8- to 12-year design life in oat (emergency power) applications at 77°F (25°C) and a 3- to 10-year service life depending on the nature of the non- oat applications, ODYSSEY batteries save you time and money because you do not have to replace them as often. Unlike other AGM VRLA batteries, the ODYSSEY battery is capable of delivering up to 400 cycles when discharged to 80% DOD and properly charged.​
  • Longer storage life
    Unlike conventional batteries that need a recharge every six to 12 weeks, a fully charged ODYSSEY battery can be stored for up to two years at 77°F (25°C) from a full state of charge. At lower temperatures, storage times will be even longer.​

What you don't want to do is store an Odyssey, really any battery, discharged. Being left in some state of discharge is what ruins batteries. Constantly floating an AGM at 13.6V up to about 13.8V will be about all you can do. I have a deep cycle Deka AGM that is well over a decade old in my ham station. It just sits there on a charger, never being cycled. I load test it once in a while and doesn't seem really any worse for it.
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If really well maintained, a true deep cycle version will likely be fine for ten years.

A proper 20-hour load test will tell you its current capacity and thus SoH.

Industry standard is scrap it at 80%, goes downhill pretty quick after that anyway.