I have a Schumacher unit I got a super long time ago when Walmart sold them. Attached to the posts in the front, battery is a yellow top optima. I'm going almost 10 years on this battery.
A month ago I tried a legit Battery Tender, and it damn near caused a thermonuclear meltdown. After an hour I measured the battery temp at 160 degrees. Tried it on a second battery and same thing.
I do drive my cars at least once per week though. That probably helps.