Generator polarizing with magneto ignition

[jOe]

Usually I use a set of jumper cables and my car's battery. That's 40+ amps. I haven't fried anything yet, but I was wondering what is the minimum amperage that will work. I think the charger I have is rated about 6-8 amps but I don't think it's enough.
Is there a spec. on this anywhere?
I'm guessing the value changes between 6V and 12V systems as does the battery amperage.

[sportsterpaul]

The field coils in the 12V generator are about 6 ohms, so that means when you put 12 volts across them, they draw 2 amps. It does not matter if you feed the 12 volts from a truck battery or a 2A charger. Polarizing the generator puts a little residual magnetism in the armature. This allows the generator to self-start when it spins. You have to get the magnetism in the right direction, or the generator will try to make -12 volts instead of +12 volts. A 6-volt generator should need 4 amperes, I assume. Your charger should work fine.

First, you need to get the field coils in the circuit, the regulator may or may not. I think the Bosch regulator does not have a cut-out relay, so its regulator relay is connected the F terminal to the A terminal even at 0 RPM. Thing is, the Bosch regulator has a resistor in series with the field coil, so I like to be sure, so I just connect a little jumper wire clipped between the F terminals on the generator and frame ground. When I ran a mag, I used my 6-amp charger. All you need to do is brush the 12V cable to the A terminal. A half-second is more than enough, if I remember right, the field coil ramps up to the 2 amps in a few milliseconds. Be sure to remove the jumper, or you will blow all the lights when the bike starts and you rev it up.

In general, the only time you need to polarize the generator is if the armature has been replaced. I did have one lose polarization because I was dicking with it, and somehow got negative voltage across it. It does not hurt anything to run the generator unpolorized. You can just start the bike and see if you have lights. If not, do the procedure and try try again.

Oh, my high-zoot Sears 12-amp charger does not work unless it senses a voltage. I guess this is to protect things if the cables touch together. You should see a little spark when you touch the A terminal, and you should see the meter on the charger do something. I don't like using jumpers to the car, since it is so easy to short the cable together and blow up your car battery. You could use 18-gage wire instead of jumpers to protect the car battery a bit against shorts.

There is a saturation of the magnetism in the armature-- its not like 24 volts will polarize it "harder" than 12 volts. You do want to get the metal fully magnetized. A brief connection of a 12V car to the 6V generator won't melt anything, but don't let it linger.

[hennesse]

Remember the old adage: If more is better, then too much is about right... Instead of your car battery, you could just use your arc welder!

Let's step back a minute and figure out what we're trying to accomplish, and then figure out the best way to do that.

What we're trying to accomplish is to magnetize the generator's pole shoes. Huh?

When new, a generator is confused about its orientation. It will gladly make electricity in either direction. We need to give it instruction about which direction to generate.

The poor, unappreciated pole shoes are where the generator stores its instruction, waiting for the next time you start your bike. The field coils (one north pole and one south pole) are held in place by the iron pole shoes. When current flows through the field coils, it magnetizes the pole shoes (one north, one south). When the generator stops turning, the field coils quickly lose the magnetic field that the flowing current has induced. But the iron pole shoes remain magnetized for years.

The next time you start your bike, it is the "residual" magnetism in the pole shoes (our stored instruction) that causes the generator to produce electricity in the "correct" direction.

We instill the instruction in the pole shoes of a "new" generator by polarizing the generator. On a battery equipped bike, this is accomplished by momentarily (like 1 second) connecting a wire between the "BAT" and the "ARM" terminals of the regulator. On a magneto-equipped XLCH, you have to supply an external battery, but it need not be any bigger than the battery in an XLH. Your car battery (200 cold cranking amps) is way overkill - the field coils in your generator only draw an amp or two. Connect the negative terminal of the external battery to ground, and touch the positive terminal of the battery to the regulator's ARM terminal for 1 second.

This instills enough magnetism in the pole shoes for you to start the bike and have the generator produce juice in the correct direction. When the bike starts, and the generator spins, it will build up some additional magnetism in the pole shoes - enough to last for years.

In case you are wondering - inside the generator, one end of the field coils is attached to the A terminal (and positive armature brush). The other end of the field coils is attached to the generator's "F" terminal, which is attached to the regulator's F terminal. At rest, the points in the voltage regulator section (of the regulator) are normally closed, so the field is attached to ground. We have a complete circuit through the field coils. Jumpering the BAT to ARM simply bypasses the regulator's cutout relay.

From Delco-Remy 1R-5134 over in the Technical: Regulators section

gen.jpg (22.87 KiB) Viewed 50361 times

If you want to polarize a generator without having a regulator: connect battery negative to generator frame. Jumper generator F terminal to generator frame. Touch battery positive to generator "A" terminal for 1 second.

A small battery is a better choice than a battery charger. Most battery chargers put out really "dirty" DC - there's a big AC component leaking through the charger's rectifier.

The residual magnetism stored in the pole shoes diminishes over time, like years. Removing the armature also diminishes it - the big iron armature kinda helps keep the magnetism in. This is true for magnetos (like an XLCH) too - if your remove the rotor from the magneto for a long time, it has a good chance of losing its residual magnetism too. Unfortunately, magneto rotors require professional help to remagnetize - see the Technical article on Magnetos for a source of remagnetizing service.

---
This residual magnetism in the pole shoes is why you can push-start a generator-equipped bike or car with a dead battery - there's just enough juice in the generator to allow it to start making electricity. Alternator-equipped bikes and cars can't do this - alternators don't have pole shoes, so they do not contain residual magnetism.

[thefrenchowl]

Thanks for all that lads,

I have reassembled my 52K generator, been about 25 years in bits in a box, for the 55KHK, but as usual, it don't work...

How does one check if the fields are wired properly to give one N opposite one S???

No battery, so it might not matter if it gives - rather than + ????

I had to redo some of the connections out of each field and dunno which is which...

Patrick, well and truly stuck... (not that it worries me to drive the bike without lecky... I can tell the cop it just failed 2 miles away.. ; O )

[hennesse]

I have reassembled my 52K generator, been about 25 years in bits in a box, for the 55KHK, but as usual, it don't work...
How does one check if the fields are wired properly to give one N opposite one S???

Patrick - check the Technical: Generators: Model 52K section. The field coils are the same, only the wire connections are different. Try testing each field with an ohmmeter. I can't remember now, but I think it should be a few ohms. Not shorted or open. After assembly and polarizing, the generator should motor as Perry's notes say. It may not motor fast, but it should turn slowly, at least, hopefully in the correct direction. If it stays "locked" in one place, and you can't turn the gear by hand either direction, it's fighting itself, and you've got something wrong. It it does nothing, you might have a bigger problem.

Hey Perry - do you still rebuild generators?

[sportsterpaul]

Arrghhhh! Thanks Dave. Rather than saying I was an idiot for saying you jump A and F together, Dave pointed out the internal construction, and yeah, you ground the field terminal if you don't trust the regulator to do it. I went back and corrected my earlier post.

This is the interesting problem with using a charger. Since it is probably putting 14 volts across the A terminal, when you apply it to the A terminal, the regulator thinks there is too much voltage, and takes the field coil out of the circuit, so you are not really magnetizing the poles. Dave has it best, just use the same voltage battery as the generator. I still like to connect F to ground, but if you use a battery and not a charger or power supply, then the regulator thinks there is not enough voltage, and it connects the field to ground for you.

The only difference in the size of the battery is the sag in voltage when you connect it. A little battery will sag down to 11 volts as it supplies the 2 amps, a big one will sag down to 11.8. They both get the job done, but the little one is safer in case you accidentally short the wires.

[jOe]

Moving on to that big capacitor off the regulator , which I recall is 450 picofarads/24V, if the relay is manually triggered, and however much is stored in it was put back into the system, would that be enough to flash the fields?
But if there's no output from the generator it wouldn't recharge anyway.

[sportsterpaul]

Sorry dude, the capacitor is just there to take the switching spikes out of the output. To my knowledge, the capacitor is connected to the armature. When the bike is off, the capacitor is discharged. Zero volts on the armature means zero volts on the capacitor. Even charged up, it is too small to supply the two amps needed to polarize the generator.

I can see you are in the "bargaining" phase of the 5 stages of grief. After you get past the depression, you will come to accept that you need to connect a lead-acid battery of the same voltage as the generator for a half second. We have all gone through it-- welcome to the club. Then again, you can just start the bike and see if the lights work. That's what I do. Polarize schmolarize.

[jOe]

Yeah, you're right. I've rarely had a problem with getting a generator to charge. And I've started out with some really rusted out hulks. I have one on one of my CHs that sat disassembled in a box for 25+ years. Cleaned it up, put it together and it fired right up.
But-I'm not going to assume that any capacitor is discharged unless I discharge it myself.
I had a couple of electroshock therapy treatments going into radar sets with that assumption.
But each time was followed by a period of calmness and well being.

[sportsterpaul]

Boy I hear ya about high voltage. I worked at Teledyne on TWT (traveling wave tube) radar power supplies. They were used in F-16 missile jammer pods. It was 10,000 to 20,000 volts. My first day I asked what the wooden handles were hanging from the ceiling. "Oh that cuts power to the whole shop floor, in case someone is getting electrocuted. You should not get anywhere near the person until power is out."

OK.

What astonished all of us is that they used metal lab benches instead of wood. They taught me all the tricks-- keep one hand in my pocket so I don't get zapped across my heart, wear rubber-soled shoes, etc. I never saw anyone get hit, but the year before a tech got tossed on his ass and knocked out. He lived, but they said he was quieter and more withdrawn for a full 6 months after the accident. He did get back to normal, but I noted that he had quit by the time I got there. I can't say I blame him.

I had this big burly biker pal tell me the only thing he was truly afraid of was electricity. When I asked why he said "Because it can kill you and you can't see it." Good point. I would not worry too much about 12 volts, but when they taught me how few milliamperes can stop your heart-- yeah, I agree, why take chances. When I worked around car batteries the rule was no finger rings, since getting a short through the ring would cook the finger it was on. Man, that is a tough way to loose a finger.