You have a few options here, but I have a few questions:
1.) What battery chemistry are you looking to charge?
2.) What do you mean by smart?
Any circuit you come up with will involve an AC -> DC circuit, these are available as complete off the shelf units aka bricks or power supplies. This will take your 240VAC and output a DC voltage. You'll probably want something in the 30VDC / 20A output range (but will vary depending on the efficiency of your charger).
From there you can create a semi discrete circuit from scratch with a comparator or use an off the shelf charger IC. Look at TI's bq series for instance. Linear tech and possibly Maxim may have solutions as well. But this is highly dependent on your chemistry. Lead acid is the easy to develop a charger for with Li-Ion and NiMh being equally challenging and dangerous if you don't know what you're doing.