Re: Re: Why 6 volt -vs- 12 volt
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Posted by JerryU on May 11, 1998 at 15:15:11:
In Reply to: Re: Why 6 volt -vs- 12 volt posted by Clinton E. Hofstetter on May 11, 1998 at 13:03:13:
: : What is benefit of 6 vs 12 volt system. I know nothing about tractors and have seen references to this. What and why is one more/less beneficial than another? If you have one, is it easy to swap to the other. I am asking because I am contemplating a tractor purchase (the referenced MF 202 with loader) and I am now wondering if this is a relevant issue with this tractor. : I don't know of any intrinsic "benefit" of six volt over twelve volt. That is the way most old tractors, as well as old cars and trucks were designed. If you want to have origional restorations you will need 6 volt system. Most tractors and cars didn't change to twelve volt until the late fifties or early sixties. There were some exceptions of course. Many times you can have the origional generator and starter rewound for twelve volt, and then change the lamps in the lights as well as a dropping resistor in the battery ignition system. Magnetos don't matter. A well mantained 6 volt system, good wires and battery cables, etc. , will perform very well. A well maintained six volt system will work quite satisfactorily as state. It has for many years. I think, and this is my opinion, the switch to 12 volts was prompted by equal parts physics and economics. In electricity, for a given load, the higher the voltage, the lower the current. This is where economics comes in because the lower the current, the smaller the wire. And less copper is quite a savings. That is why a 12 volt starter cable will not work adequately on a six volt system. It is only half as big ( and should cost less). The six volt starters, generators, and devices have more copper to carry the extra current. The second portion of the equation, the physics part, is that a 12 volt system is a little more forgiving. When current flows through a conductor or connection, or device, like a battery, there is a loss due to heat. The formula is current squared times resitance. This equals the loss in heat energy. (watts) Since the six volt system passes more current, a given resistance (ohms) will generate quite a loss. Lets take a quick look at a connection with a 1 ohm resistance drawing 10 amps. That 1 ohm will generate 100 watts of heat. -- quite a bit. A twelve volt system powering the same load will only draw half as much or 5 amps and produce a 25 watt loss. Since everything has resistance, the 12 volt system becomes more forgiving, generating less heat loss, delivering more oomph to the starter. So much for a short explanation. Hope this helps out on the "why" JerryU
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