I've had the
Solar BA-9 for about 8 years. I check all my cars at least 1x per month and help others. Nice to see when starting to drop.
I think others here also recommend
Ancel BA101
I got the BA9 after watching the battery videos from Kent Bergsma (mercedes source) on a YT. I also got the CTEK 7002 charger after watching a bunch of videos and the one from Optima batteries when they showed it working to recover a dead spiral cell that others wouldn't charge. I had 3 spiral deep cycles at the time and all needed a charge at least 1x per year do to the very short trips. I use it for my batteries now as a nice solid overnight when I remember