Back in the late 60s and early 70s, I saw many A-D trucks in VA that had 12 volt replacement cables. The shade-tree solution to starting in those "cold" VA winters (6 degrees warmer than Hesston, KS) was an 8v battery. I kept my 6v battery charged because I knew nothing about 6v vs 12v battery cables, etc.
I now live in upstate NY. It gets a little cold here in the winter (7 degrees colder than Hesston, KS - usually a low below 0 around February 1st). With proper battery cables (both leads), clean connections, and a 6v Optima battery, my Suburban starts in Jan/Feb (after sitting without being charged since November). My garage is detached, unheated, and provides excellent winter cold-storage.
I have done this start-up test during the last two winters (7 year old battery, with no battery minder) - just so I know the truck will start in the coldest weeks of the winter.
Sure, a 12 volt conversion provides better cranking (but it is no longer a 6v truck). If a 6v battery does not crank in the cold, there are problems that need to be corrected. An 8v battery will work fine, but if it is needed to reliably start a 6v truck, it is a band-aid covering other inadequacies.
I get along with whatever someone wants to do. But, I only post like this in response to a solution to a problem that would be solved with a properly maintained system (as it was designed for reliable performance).
