Review on Battery Tender Plus 12V Charger and Maintainer | Motorcycle, ATVs, and More - 1.25 Amp Automatic PowerSports Battery Charger | 12V Battery Chargers - Model 022-0185G-DL-WH by Mark Quarterman

I have 2 cars that aren't driven much: a 2008 Corvette and a 1966 Mustang. The Vette has an Optima AGM battery and when it sits for 2 weeks the voltage drops so much from parasitic discharge that it just clicks and won't start. On the other hand, the Mustang can sit for a month or two and the battery will still be strong. So I needed something to keep the Vette going and this battery tender seemed to fit the bill. Come on. The manual says the green light should flash when the battery is over 80% to let you know when the battery is usable, so I figured it should light up. I checked the voltage and the battery was up to 12.9v so I knew it was charging but there was still no indication that the battery was more than 80% charged. I waited about half an hour and finally the green light started flashing for about 15 minutes and then came on, which means charging is complete. I then tried this on my Mustang's lead-acid battery, which was also 12.6v, with similar results. The yellow light stayed on but no green light even when the battery hit 13.1v. I got tired of waiting for the battery to hit "80%" so I checked it after an hour and by then it was fully charged. I unplugged the tender and after 24 hours the two batteries were back to 12.6v. While it charges and keeps the battery charged I am disappointed that the flashing green light only comes on for the last 15 minutes of operation. Charger. I can't believe the battery is less than 80% charged at this point. So yes, Battery Tender seems to be working, but the 80% progress bar is pretty much useless to me.