I am sure I have killed a few batteries with my old charger (that has now gone to the great car boot sale in the sky). I bought one of those CTEK electronic things (well actually it is a cheapo knock off) but it has been brilliant.
It looks a bit like "the good ones"
It detects knackered batteries
It detects incorrect connection
It has a bring it back to life mode that I am sure saved my current battery after about a year of no use