Join Date: Jun 2018
Location: Long Island, NY
I lost a battery in the past (different bike years ago) with my Battery Tender Jr. It has since been replaced. But I have learned my lesson. Don't just leave a battery tender attached to a battery and ASSUME it will kick back on. My tender said it was fully charged, but once I unplugged it then waited until the red light is flashing and plugged it back in it showed that the battery was <80%.
So, my practice is, once a week or once every two weeks, I unplug my tender between the tender and the battery, wait a minute then reconnect it. So, even if the tender fails to identify the drop in battery, I wont lose my battery.
So, to sum it up, sometimes a battery tender may not identify that the battery's voltage has dropped below the 80% mark, unplugging and plugging back in the battery can help.
(I have a historic car, so I have a few tenders)