6 - 12 volt conversion

It takes more finagle to make a 6 volt regulator and generator work at 12 volts than most would do. With no changes to the generator it has to turn nearly twice as fast to make 12 volts as it did to make 6 volts so you don't get charging while putting around at fast idle. Changing the regulator probably can be done by adding or changing a resistor. Maybe by changing a spring, but then 12 volts on a 6 volt regulator winding are probably going to cook it to death with 4 times the power dissipation. You could change to a 12 volt regulator with the 6 volt generator but you still have the needing to run faster.

The starter is least bothered by 12 volts, needs no changes, but its a lot more powerful on 12 volts and battering the ring gear isn't out of reason. If the engine runs on a magneto for ignition, the 12 volt starter may spin it just fast enough the impulse start mechanism doesn't work but its not really fast enough for regular magneto function to make starts a little poorer.

Does it really have a regulator or is it just a cutout with just two terminals? A regulator needs 3 because it does the cutout as well as the voltage regulation function and so needs a connection for the field. Some regulators have 4 to allow light switching automatically by the regulator to keep them off when not charging.

You also need to change the coil or its circuit to use a 12 volt coil or a resistor on the 6 volt coil primary, else point life and coil life is short. Often you also need to swap the primary connections because 6 volts was positive ground and 12 volts is negative ground, especially when a car alternator gets used for usually much much better battery charging. The modern solid state regulator of the alternator treats the battery much better by not overcharging like the old regulator was allowed to do, by loose SAE specifications. And the alternator treats the battery better by not drawing 10 amps reverse current to trip out the cutout.

You can buy electronic regulators in a case to look like a vintage regulator and a diode cutout in a case to look like a magnetic cutout to get the improved regulation and the lack of reverse current. Even from vendors on this forum.

Do you have an ammeter to judge charging? Does it start charging at some engine speed and then taper off the longer you run it tapering to zero, or does it hold at 15 or 20 amps, diminished only by lighting loads when the lights are turned on?

Gerald J.

6 volts worked for decades. Just it takes more maintenance. There's no tolerance for slightly corroded connections at 6 volts, so you have to clean battery posts and connections regularly, like every 6 months if you want reliable starting. You can't go buy battery cables at wallyworld's battery kiosk of #4, you have to go to NAPA and plunk down real cash for real #0 or 00 battery cables. Then you can't safely jump from a 12 battery to the 6 volt, one of them can expand uncontrolled spraying you and the equipment with sulfuric acid and bits of flying lead.

There is less traffic in the stores selling 6 volt batteries so they tend to not be on sale and to have sat around a long time. Way back when 6 volt batteries were the standard, they were kept on charge in good stores so they didn't go bad from sitting, but even then finding on with a recent manufacturing date was a definite benefit in long life. So its possible to have to buy a new 6 volt battery more often than you wish because it was junk out the door.

As I mentioned the vintage SAE standards for voltage regulators were loose enough that one might never charge a battery fully, and the next might always overcharge the battery.

I put lab quality voltmeter and ammeter in my '64 VW about 1966. About 1968, I swapped engines and built my first solid state voltage regulator. The next new battery lasted about 6 years because of proper regulation and picking one at the store with the most recent manufacturing date. The voltmeter and ammeter showed me things about the mechanical regulator that I didn't like, such as drawing 8 amps from the battery as the engine speed went down before the cutout disconnected the battery. When not driving hard (not hard to drive hard in rural Iowa, but tough in suburban DC on an Army post) that severly interferred with good battery charging. The solid state regulator with diode cutout or the gaggle of diodes in the alternator give the same results, no back current into the dynamo at any engine speed. And in my bug regulating a 12 volt generator to 6 volts made it charge at slow speeds like the modern alternator.

I also learned from that bug that the voltmeter gave far less useful information than the ammeter. That having only one I learn much more about the battery condition and care from the ammeter than the voltmeter.

Gerald J.

I have a CA that has been running on 12V for 15 years. I have no idea how old the starter is. When I overhauled the engine, I put a new ring gear on it. A 6v generator will easily produce 12v with adjusting the voltage regulator spring. I know, I've done it to see if it works and it does. The regulator won't last long on 12v due to the higher field current. Burns the points, overheats the electromagnet. Going to a 12v regulator and a 6v generator doesn't last long either, found that out too. To make it work, you have to change the fields in the generator to 12v, or find a 12v generator. My CA has a D17 12v generator and regulator and my Oliver 60 has a 12v generator and regulator from a diesel 77.

You're forgetting Ohm's Law. When you double the voltage, you're also doubling the current. Remember that when the load is the same as in a 6v starter, half the current is required to do the same work when the voltage is doubled. That's why larger cables are needed for a 6v battery to crank an engine at 6v than when a 12v battery is used to crank the same starter/engine combo. You also have to remember that an alternator is 3 phase with a full wave bridge while a generator is single phase. Having the larger diameter rotor that is only a magnet provides more peripheral speed cutting more lines of flux than a smaller diameter armature contributes greatly to the efficiency. A generator only has 2 poles while a rotor in an alternator has many  north south poles. The only benefit to the commutator is it's much more forgiving than a diode.

All I can tell you is I have a WD45 that was converted to a one wire Delco altenator in 1980. Somewhere along the way the resistor went bad and I switched to a 12 volt coil. I use points and condensor for a D17 but I can't see any difference from the originals. I have never had a starter problem since the upgrade and it has the original ring gear. It ALWAYS starts.

I've always preached that the 6V system works fine with proper care and maintenance, but does have its limits as far as accessories added. Adding winches, stadium lites or whatever brings the stock 6V system totally out of its realm for suppling enough power for the accessories added. One or maybe two 6V work lamps added to a Tractor equipped with headlights and a tailamp and Battery Ignition is about the limit for the 6V system as far as keeping it in check. In some cases where a three brush gennie is in service, a little adjustment of the third brush can compensate for the extra load items. Most customer's that inquirel about our 12V conversions complain that the engine doesn't turn over fast enough with the 6V system. Usually, thats a worn component problem somewhere in the system. (ie starter, gennnie, bad battery etc.) When the 6V system's components are in good working order and condition, the system will work flawlessly. The 12V conversion works nice when those extra lamps, winches, and accessories like those are added. Just remember though, when using large draw accessories on any 12V system, if using a standard push/pull or toggle switch, use a relay downstream to handle the switching load. This takes the load off the toggle or push/pull thats only rated around 10-15 amps. Your electrical system will thank you for it being more reliable and give you many years of service....

But the battery would give away the conversions. Likely the current rating of the garden tractor generator would on the low side taking hours to recharge the battery from a normal start.

Gerald J.