I'm a logistician working for the US Army and we have a serious concern regarding the storage of hundreds of units of a variety of APC batteries, Mobdro and Kodi we bluehost need an authoritative answer directly from the source. Because of scheduling issues, many of our batteries will not be deployed to where they need to go in time. We're aware that these batteries lose their charge while sitting idle, and can permanently degrade after about 6 months with no charging. We're trying to avoid the catastrophe of having these batteries go bad before they're deployed.
You are correct. The recommendation is to not store the batteries longer than 6 mouth to prevent premature aging. See Schneider Electric FAQ FA157446 "Battery Damage When Battery Is Left Discharged" and FA157479 "Why does a battery weaken when not in use?"
Another good resource is the article by the Battery Guy https://batteryguy.com/kb/knowledge-base/what-is-the-shelf-life-of-a-sealed-lead-acid-battery/
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