Originally Posted by 
DiscoMick
				
			 
			Sorry if you've already answered this, but do you have a good dual battery controller such as a Traxide? If so it should charge the starting battery quickly to 80% and then connect the two and charge the second, although at a slower rate. The Traxide also allows some drawing of the surplus power in the starting battery, but retains enough to start the vehicle. Works for me with an original size Varta starting battery, the Traxide and then a 60 amp fused cable to a $300 Kickass 120Ah AGM in the back, which will run a 35 litre Evakool fridge for at least 3 days.