Nas, you only need a power supply if you're using 240v supply and your charger is 12v only. If your charger does both then no psu needed.
I may well be teaching you to suck eggs... but 240v is mains power and 12v is car power.
Use these
http://www.ebay.co.uk/sch/i.html?_tr...at=0&_from=R40 to charge your 12v car battery at home