Hi! Based on what I have read. If I am not mistaken your alternator is gone. If all your electric indicator on your Dash Board is not functioning and your lights are going dead then alternator is not charging the battery. You have said you have fitted another battery but it happens again. This is an indication that battery is not charge by the alternator. Normally when you SWITCH OFF all the lights, radio, heated screen and heater the battery should charge the minute u start the engine.
Hope this will help.
I like Diesel Engines, February 2009