electrical/charging/2nd battery

hay all can anyone help out with this one....?
i want to charge a 2nd battery in the back of my landy but dont wanna pay money or get to technical....so was thinking of hooking up a 2nd alt thats the easy part the hard part is understanding the electricals lol.

can i just run wires from 2nd alt to batt..?
would it over charge the batt..?
would i have to fit some kinda shut off switch...?
would it blow the batt up..?:doh:

i have been down the rd of buying the split charger but its a landy things dont stay in the right places for long ....when having fun off rd/greenlaning wires break....and they only seem work if you have 2 brand new battery's im trying to do things on a shoe string...
so if anyone can give me some help on the matter id be happy thnx in adv.....

I WOULD RATHER PUSH A LANDY THAN OWN A JEEP!!!

Split charger is the way to go. Alternators are expensive, easily damaged off road and what makes yu think wires wont break on an alternator system?
Just do the job propper and it will be ok.