Ponty
pfm Member
That sounds strange to me. I would think it is the same if you connect the Earth to the battery or the chassis, since they are joined to each other with a strap connector. In all the 50 years I've been charging batteries I've never noticed any difference if I disconnect the battery or not, apart from having to re-set the radio stations.
This is how the manual in my Subaru XV (2019) tells me to do it, as well as the CTEK manual. Disconnecting the battery to charge is a world of pain apparently.