I don't know, all I can say is that my brand new battery was on the Battery Tender for a few months in the garage, properly watered, and 24 hours after removing it from the tender the SG was only 1.225 or so. The voltage was about 12.3v. My guess is that even though the battery is new, it was was somewhat discharged when I got it and the tender is just not an adequate way to fully charge it. Might work fine to maintain a fully charged battery, but don't expect it to ever bring a somewhat discharged battery up to 100%, no matter how long it is connected.
