Selfsufficientish.com

Hi everyone,
I haven't been around here for quite some time so I hope you don't mind me hopping on and asking a question or two. I was chatting with someone today who suggested rigging up solar panels to car batteries. Do you think this is a good idea? Would it work in a 4 bed home? How much of our power could we expect to produce this way? Could you link it up to the mains somehow so that we used the stored energy from the solar panels, but when the batteries ran out we could switch to mains? Have any of you got a system like this or seen one set up in anything larger than a van? And finally, is it efficient to buy second hand solar panels for this and what is the best wattage/voltage? Thanks so much, hope you don't mind all the questions, slightly more than two! Helen.

Common in Oz to have vans, caravans etc. hooked up to solar recharge systems (in fact it is now uncommon to NOT have it). These normally power a small 'fridge, water pumps, lighting, computer, entertainment etc. However, normal car batteries are simply not good enough even for these usages as they drain quickly (they are really only designed to supply cranking power and some minor short term items); deep cycle heavy duty batteries are essential.
These cost around $A500 each for mid-quality. Typically 120 - 200 watt portable solar panels are used ($ 200 - 300) and a charger ($ 400 upwards) and an inverter to convert 12V to 240V (if you want one) ($200 upwards).