i am going to buy a battery charger that will do my van as well as my Omega if required, the problem i have is that when im looking for one in argos i dont know which one to buy. so ive picked one that will do from 1800cc to 3000cc, but is the engine capacity really relevant when chosig these or is it another scam to get more money from me? years ago any 12v charger would have done the job, so why the difference now?
help me !!!

You can always keep an eye out at Lidle & Aldi. Every now & then they do a cheapo version of a smart charger for about £13. I leave mine permanently connected to my caravan's battery when it's on my drive. It's not quite as smart as a Ctek, but very well priced.