I have used Battery Tender brand for years, I did have an issue with my wife's M3 this year to where the battery tender was on the car and the battery still went dead. Not sure why battery was not that old so I switched to Noco and it revived the battery as it appeared it did a better job in charging and maintaining the battery. Battery Tenders are good but I have had an issue so I have switched over to Noco with no regrets. I will be honest I will use and be loyal to a brand but as soon as it fails or does something that I do not like I usually look for other options... Live & learn!

 

https://www.batteryminders.com/

 

I had one of BatteryMinder's units on my Supra for I think close to 15 years. The battery contacts were corroding bad after one battery recently started to corroded and created a fair amount of blue/greenish colored crusty stuff on the positive contact. I suppose I could technically get new contacts and it would work fine as I still have it. I replaced it with the Battery Tender below...


https://www.batterytender.com/