Oldtech. I disagree on the fact 6V is cheaper. You priced welding cable Lately? 6V needs twice theamps to do anything than 12 V needs,and all those amps need the bigger cables. More volts with same or less amps can use stock cables. 12V is perfectly fine with the 2 ga cables available from Farm & Fleet or Fleet Farm.
Back around 1988 or '89 my Super H would not start. I pulled the starter and brought it home and tested it with every test in my Ford service manual, it failed every test! WAY too many slow grinding starts where it barely rolled over from cylinder to cylinder finally caught up with it. I found a reconditioned starter at a salvage yard clear across the state of Iowa. UPS got it clear across Iowa over Monday night but the stinking terminal I drove out of could NOT get it off the truck for East Moline and onto the downtown Moline truck! I even gave the girl who clerked at night the truck number and drivers name! The clerk was pretty but dumber than a box of Rocks! Anyhow, Friday night I drove down and finally got my starter. Took it out Saturday and put it on, and tractor started up better than any time since we got it in 1968. Think it was that fall or winter Dad converted it to 12V alternator.
Fast forward to last summer, new 12V 1000 CCA battery, alternator charges 25-30A after start-up, cables are fine, but tractor barely turns over. FONDYAuto Electric used to have a shop here in Madison but they now pickup and deliver at another company here in town. All work done in Fond DuLac. My starter according to the tech at Fondywas poorly rebuilt way back in the 1980's. The brusheswere running off the commutator. They cleaned it up, new switch, brushes, bendix, greased & oiled, tested and $140 later I put it back on. It spun over so fast it scared Me! When I let off the starter switch the engine actually slowed down to a 600 rpm idle. Bet I didn't hold the switch down even a full second! So I will agree, you need a good starter for Anything to start reliably. But anything 6V will or can do,12V will do better, about TWICE as good actually. I just checked, Blains F&F don't even show a 6 volt battery on line, Mills Fleet Farm does, but they cost as much as a 12 volt soyou get HALF the starting energy for the same money as 12 volt. It's amps times volts equals watts which is essentially Horsepower. To get equal amps times volts you need TWO 6 volt batteries.
So we agree on the fact you need a good starter. You need a good alternator. In the millions of miles I'vedriven I"vehad 4, "Four"alternators fail, Wife had one. So 5total. I think that's a pretty good reliability record. Back in the generator days every town of any size had a shop that fixed starters and generators. Even the town of 100 people I grew up by had that shop. And every other town around had one or two also. Plus the Big shops in the bigger towns and cities. Now days that BIG shop is the only one still around. So even with several times more cars and trucks on the road and many times more miles driven alternators are much more reliable than generators and the one repair shop can keep up..
I guess it depends on if you want a toy to play with or a tool to use and depend on.REICHOW and I want the tool that has as much in common with everything else as possible. I have to laugh, I called a Deere 4010/4020 diesel "Starting Aid" one time on here "A FARMALL H or M with a log chain to pull start it." That silly 24V starting system was Not a better idea. Tookthem till 1969 to realize that a normal 12V with alternator and two big batteries to get enough amps was best. First side console tractors were first 12 V start diesels. Dad probably didn't buy the best batteries, but batteries overall were not good in the 50'sand '60's, if our4010 sat for more than a week we'dhave to mess with it to get it started.
Anyhow, I'mdone. If 6 volt was so good companies would still use it. And nobody does.