All the electric conversion questions made me wonder about some tractors I switched to 12 volt for myself. I use a properly sized fusible link for 10 guage wire at the point my wire leaves the point of battery cable attachment and goes on to the ampmeter. Then use a fuse for accessory wires. My question is when the alternator is sending the current back to the battery is the fusible link doing any good or necessary? Only used alternators from older general motors with internal regulator rated I think from 37 to 42 amps so far. If the battery would get real low would they charge enough to melt the fusible link? Never happened for several years.
- Thread starter D Slater
- Start date
I would day the alternator has its own current limiting control (thats the function of its internal regulator) to prevent excess current to the point its damaged. Its important the VOLTAGE SENSE circuit is intact (wires to the #2 small side terminal, senses batetry voltage so it knows if its low or high n needs charged or not) because if it sees low voltage it tries to crank up the output.
Theres more but were headed to Church so I gotta run
John T
Theres more but were headed to Church so I gotta run
John T
Brownie 450
Member
I always put in a 40 amp circuit breaker right off the solenoid batt terminal. I run a #16 wire back to the same point for the voltage sensing terminal as John was talking about. The voltage sensing needs to be connected as close to the battery as feasible. Those who connect a short jumper to the alternator output terminal are actually reading out alternator voltage instead of battery voltage.Not much difference, but still some. However, most people seem to get by with the short jumper.
Bob M
Well-known Member
Alternators are inherently self-limiting for current. Even with the output terminal dead shorted to ground an alternator will not provide more than rated amps as stamped on the case.
And a #10 wire carrying 42 amps may get a bit warm but it won't melt/burn even with a 42 amp alternator at full load.
However your #10 wire COULD melt/burn should a short develop at the ammeter or wiring between the battery post and the ammeter. The battery could send several hundred amps thru the short which will quickly melt the wire.
Fortunately a short like this is not likely - but it is possible...
And a #10 wire carrying 42 amps may get a bit warm but it won't melt/burn even with a 42 amp alternator at full load.
However your #10 wire COULD melt/burn should a short develop at the ammeter or wiring between the battery post and the ammeter. The battery could send several hundred amps thru the short which will quickly melt the wire.
Fortunately a short like this is not likely - but it is possible...
A diode in my H alternator shorted and burned all the 10 AWG insulation and melted conductor two. If a diode shorts in the alternator there is nothing to limit the current. This happened when I was not around, I never smelled the smoke or saw the flames. The wiring was fine for 25 years, then one day while walking by I noticed the damage. A fuse or breaker would have saved the wiring. I use a 30 Amp breaker on my H with a 12 Volt generator and a 60 Amp breaker on my H with an alternator.
Charles E. McNelly
Member
What brand of Tac is that on your tractor?
Charles
Charles
Ten gauge wire is protected from battery current by the fuse link wire installed to the ten guage wire and the positive cable at the starter switch. The link will give out before the ten guage wire melts. My question, is the fuse link doing anything to help protect the wiring from the alternator back when its charging? If the fuse link overloads and burns out my alt. exciter curcuit would go dead. Then if the ten gauge wire back to battery from alt. is open or disconnected due to the fuse wire burn out. Will the alt. output then stop? Or will overload of the ten gauge wire stop? Thanks for the information.
Yes, the fusable link is doing something. If you were to develop a short between the alternator and the battery it could short out your battery before it frys the wire. Therefore, it is definately doing something. We experienced this with a soil sampling machine on an ATV at work.
One way to check the H speed going by RPM is to figure the overall gear ratio in 5th. Its 16.83, multiply by 168, = 2827.44. Check the radius of tire used, I use the measurement from center of axle to ground with tractor weight on the tire.
Multiply the RPM you are turning and the radius measurement. Say you turn 1600 RPM, multiplied by a loaded tire radius of 28.6, that = 45750. Divide the 45750 by whatever gear ratio you use X 168. In this case 2827.44 divided into 45750 = 16.18 MPH.
Some use tire diameter, so 336 instead of 168 would be used. Hope I didn't mess up in explaining that.
Multiply the RPM you are turning and the radius measurement. Say you turn 1600 RPM, multiplied by a loaded tire radius of 28.6, that = 45750. Divide the 45750 by whatever gear ratio you use X 168. In this case 2827.44 divided into 45750 = 16.18 MPH.
Some use tire diameter, so 336 instead of 168 would be used. Hope I didn't mess up in explaining that.
"Even with the output terminal dead shorted to ground an alternator will not provide more than rated amps as stamped on the case."
Actually, in most cases, and alternator with the output dead-shorted to ground would produce NO current and NO voltage (unlike a DC generator).
Actually, in most cases, and alternator with the output dead-shorted to ground would produce NO current and NO voltage (unlike a DC generator).
Janicholson
Well-known Member
Hooking a battery up backwards will take out the fuse link leaving the alt intact. A shorted diode pack in the alt will also toast the link, not the wiring. To me it is a must for reasonable safety. Jim
teddy52food
Well-known Member
I wonder??? If you hooked it up backwards there would be a flow enough to heat up and open the link. By then I think the diodes are toast.
The ORIGINAL 10SI regulators were voltage protected in that if the voltage sense line became disconnected output voltage would rise only a Volt or so above normal. I've heard some replacements from "the land of almost right" may NOT be set up that way.
If the fuse link in the charging wire fails while the alternator IS charging, output voltage would continue to be regulated by the internal regulator, with field current provided by the diode trio.
If the fuse link in the charging wire fails while the alternator IS charging, output voltage would continue to be regulated by the internal regulator, with field current provided by the diode trio.
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