Fitted om a 94 300tdi, is too small, One year old, reading 12.7 volts on saturday, air temperature reaches minus 7 on monday morning, it wont start, not enough juice to crank the engine. It snows monday afternoon, could have done with the disco. Battery is a 68amp hr, 072 supposed to fit but thats only 70 amp hr. Does that make much of a difference when fitted or is there a better alternative.