I have an 81 VW rabbit with 16 6v golf cart batteries. 8 batteries in the engine compartment and 8 in the trunk. With new batteries it has a range of 40 miles. It is time to change the batteries. Is there any more modern battery that will be a direct replacement that I could double the range? question 1: is it possible? Is it economically feasible? I guess I am asking if there is anyway of getting twice the range for twice the cost of what the replacement for lead-acid batteries would be?