My dad went to an 8v battery in the Farmall Cub he had and used at the ranch...95% of the Cubs (think it was a Cub if I recall) running was at idle, pulling a grape trailer as the pickers were dumping the baskets in the trailer, seems the generator just didn't give out enough juice at idle for the extended periods of time it was run...seemed like every other day we'd have it on the charger to get it fired up, the 8v battery solved that issue.
I know he did adjust the regulator, maybe that helped?...or maybe the 8v battery had more reserve?...I dunno, but from that point forward, we always put 8v batteries in all of our 6v farm equipment.