Electrical ?

[Animal]

I don't know an ohm from my elbow so I would appreciate it if you can straighten me out on this. On the new cars the battery cables are very small and they are 12 volt systems with electronic ignition and power this and that. How come on an old tractor that you convert to 12 volts that you still need cable the bigger the better when you use just a starter and coil, and most the time the starter is a 6 volt starter. What is putting such a load on it that you can not use the smaller modern cable? Thanks in advance!
 

[Bruce (VA)]

" How come on an old tractor that you convert to 12 volts that you still need cable the bigger the better "

You don't. The smaller cables used on 12v cars work just fine on 12v tractors.
75 Tips

 

[Royse]

Newer cars, newer technology?
I've never actually measured the current draw on the starters, but it's
possible the newer starters, specially gear reduction ones, draw less power.
As Bruce said, I've used the smaller cables on 12 volt conversions.
They work fine.
But if you have the large cables, and they're in good shape,
I wouldn't spend any money to change them.
The larger ones don't heat up as quickly.
The only drawback to them that I can think of is that they are stiff.
 

[Animal]

Bruce, don't think that I am doubting you because I am not. I just read on one of these forums a few days ago how much easier a tractor would start using bigger cables and that put me to wondering why.
 

[JMOR]

[Jubilee85]

think of you trying to put out a fire, you got a garden hose and you are doing a fair job, then someone gives you a hose that is a little bit larger, like a 1" hose, (old one was standard 1/2")the amount of water is far greater, more flow. The pressure could have changed too.
In electricity, water flow is kinda like amperes, and water pressure is like voltage.
the two combined make the big picture. In electricity this term is Watts ( total power)
If your starter on your tractor needs, 100 watts of power to do its job (number made up) - the old 6 volts X 16+ amps would be the amount of total power, but if you changed to 12 volts, the amp load would have gone down to 8 or so. The larger cable you are thinking about are needed due to the larger amp flow ( think water flow) for the 6 volt. New cars have the same ol batteries but the starters are probally easier to turn over the engines might be easier to turn over so the amps could be less.
the ol adage "bigger is better is true in elecrical terms......HTH
 

[kylemorley]

With the caution that auto manufacturers don't like to waste money on unnecessary copper so the the OEM cables on 12v installations are often the smallest that will do the job, most of the time. So if you are replacing cables on an 9-2-8n converted to 12V you don't have to use big 6v cables, but something larger than the minimum size Fred's Home and Auto is selling might not a bad idea.

I used to do oversized battery cable installations for Piper aircraft. These had the battery in the back seat, and used aluminum cables. Going a size or two larger, and using copper instead of aluminum, would totally transform cold weather starting with no other changes.
 

[Plane Bart]

The lager cable carries the current flow (amps) better
Rule of thumb in electrical work the higher the voltage the lower the amperage.
 

[old]

Big cables are for 6 volt system where the amp draw is twice as high as 12 volts. I use the auto type battery cables on my tractor that have been switch to 12 volts and never had any problems
 

[Royse]

[souNdguy]

how much power does that starter take.

P=EI

use the power as a constant and re do the calcs see what happens 'wink'
 

[Royse]