If I were going to hook my $100+ battery to a charger/maintainer ..... it wouldn't be a $10 Harbor Freight version.
You can get several different brands of decent quality for around $30. I have this one I use on my motorcycle that cost $50
Charger/MaintainerThose $10 Harbor freight models will not charge a battery if it is under 9 volts. The extra money for the one I linked will charge a battery from dead. It brought both of my batteries on my diesel truck back overnight when I killed them by leaving the switch on.