I’ve got at least a half dozen of the Deltran Battery Tender Plus and a few of their 6v/12v chargers/maintainers for other applications around the yard. Some of them are coming up on at least 12 years old. Only ever had one fail. Some were made in the USA others are now made in China I think, but they’ve been reliable for me.
With the Vipers, I just wire in the quick connection under the hood and run in there. Easy.