It sounds like your mechanic knows exactly what he's doing. Do you also tell your doctor how to run his business?
"Maintainers", trickle chargers, etc. can often do much more harm than good. If you're that unsure about the guy's competence, why not pull the vehicle out and do the work yourself? A customer of any shop I ran would find his car parked on the street with a request to take it elsewhere if he pulled a stunt like that.
Jerry
