Cutout Relay vs. Voltage Regulator

ok - I started looking into what I need for the 48 super A 4H project, in the way of wiring.

First thing I'm hit with is a contradiction in info on serial numbers and whether or not it's supposed to be a cutout relay or a voltage regulator.

The place I'm looking at for parts is telling me it should be a cutout relay based on the tractor's serial number.

It HAD a voltage regulator on it to begin with - though when I got it - the electrical system was total junk and the regulator was obviously a newer add on.

I'm not even sure what a cutout relay IS - as compared to a voltage regulator.

So if somebody could explain, that'd be helpful.

(sounds like a janicholson question...)

And does anybody know if there's a definitive way to know what it's supposed to have based on model year or serial number - or any other way?

It's a 48 - 6 volt and staying that way. It's got a push pull kill switch. wico magneto. Generator looks orignal but don't know. 3 position light switch.

if any of that helps...

Assuming the 3-position light switch is original you Super came from the factory with a voltage regulator. (A cutout-equipped tractor will have a 4-position (L-H-D-B)light switch)

Forget about installing another cutout - it's WAY obsolete technology.

A cutout is the crudest way to control the generator/battery - it depends on knowledge and attention of the operator to manage the battery charge rate. Manage it wrong and you wind up with either a dead or a boiled (chronically overcharged) battery.

A regulator on the other hand automatically anytime the engine is running. Your battery will thank you(!)

A cutout relay is in effect a one way valve for the generator. When battery voltage exceeds the generator voltage, the relay prevents the battery from discharging into the wires of the generator to ground.
When the generator voltage exceeds the battery voltage, the generator can charge the battery.
(voltage and rate control are not included)
A good cutout relay is equivalent to a high amp capacity Diode. When the generator was the only option, Solid state power capable diodes didn't exist. Thus a device that latches on when gen is higher than bat, and tripps off when it is lower.
There are windings for both voltage and current surrounding the mechanism and when it detects reverse flow, the coils magnetism push the contacts apart.

A voltage regulator includes a cutout relay as an integel part. But the voltage control is separate from the cutout in every way.
The "A" style generator uses a grounded field. (supply in in the gen)
The regulation is based on a relay that opens and closes a set of contacts that ground the field. As they vivbrate several times per second, the field strength is made to fluctuate.
This variability controls the voltage output of the generator. As the out put gets to the desired charging voltage, the relay vibrates more, reducing the field current. If the load increases (lights turn on voltage goes down) the contacts stay together longer allowing higher output voltage (keeping it charging)
The cutout relay system depended on simplicity again, due to cost a simple low output generator was used that could only charge enough at full output to run the lights and charge nominally. Thus when the light switch (on many old tractors) was connected to the generator field, the generator is able to make full output when the field is directly grounded. (The light switch is not internally electrically connected to the gen. only the shaft is controlling two separate switches)
When on L (low charge) the switch causes the field grounding current to go through a 2.5 or so resistor.
In all other positions the field is full ground.
on H the charge rate is high (for recharging the battery when it was cranked too long, or started repeatedly.
On L or H it is also full ground, max output.
The cutout prevents draw when shut off as described above.
Regulators provide automatic charge regulation, better battery life, and less operator spawned errors.
If the tractor has a LHDB switch it likely had a cutout. If it has a 3 position it likely had a regulator. (no guarantees on an old tractor, but the serial # break should be good to assess the issue. Best of luck with the project, a worthy effort. Hello to all,
Jim

(quoted from post at 14:01:58 03/20/12) Assuming the 3-position light switch is original you Super came from the factory with a voltage regulator. (A cutout-equipped tractor will have a 4-position (L-H-D-B)light switch)

Forget about installing another cutout - it's WAY obsolete technology.

A cutout is the crudest way to control the generator/battery - it depends on knowledge and attention of the operator to manage the battery charge rate. Manage it wrong and you wind up with either a dead or a boiled (chronically overcharged) battery.

A regulator on the other hand automatically anytime the engine is running. Your battery will thank you(!)

Click to expand...

When I drug home my 1940 H 13 years ago, it still had the cutout relay, but non-functioning. I had this crazy idea about keeping the tractor as original as possible, so I hunted down a WORKING cut-out relay. The charging system WORKS, just as it did 72 years ago, but it's kind of a hassle remembering to move the switch from HIGH charge to LOW charge. I'll leave it alone for now 'cause it is working, but If I had it to do over again, I'd install a true voltage regulator.

So the only way a cutout relay tractor doesn't overcharge the battery is because it can barely put out 6.8 volts?

The cutout doesnt make the voltage the generator does it just closes the connection when the gen charges.

The tractor left the factory with the cutout and a generator that had the third brush adjustable for a higher charge if needed later on I-H went to a reg mounted below the gen where the cutouts were sadle mounted. I have several cutouts on my As and Bs they work just fine seen a 47H sell other day still with the cutout very original tractor.

AS usual, I agree with my sparky friends Jim and Bob so will just toss in my shortened version.

The Cutout Relay is effectively between the gennys output (ARM post) and the battery. Once the genny is running and charging it closes so the genny can charge the battery. When the tractor is shut down it opens otherwise the battery would discharge via the genny very quickly and the gennys get hot.

If it only has a cutout relay, you need a way to regulate the charge rate so the LHBD switch did that by manually setting it for LOW or HIGH charge.

The more modern Voltage Regulator had an internal cutout relay PLUS it automatically controls the charge rate so the operator doesnt have to choose between low and high charge.

If youre a purist and insist on originality you would use a cutout relay and LHBD light switch iffffff the tractor originaly had it HOWEVER if you want her to automatically charge at a more correct rate you could still use a VR even if it had the cutout originally.

John T

Great info here guys, not that I expected anything less.

Sounds like a voltage regulator is the way to go. I want the tractor original, but it will be used quite often by some of the older kids. Simplifying the battery charging would seem the best idea.

Thanks!

On High charge (no lights on) or D or B positions if the lights do not work, the gen can put out more than 7.2 to 7.3 volts. Probably as much as 7.5. This is to quickly charge the battery if low, or to run the lights if they are on. The operator is the regulator with 2 choices. Jim

(quoted from post at 15:11:59 03/20/12) The cutout doesnt make the voltage the generator does it just closes the connection when the gen charges.

Click to expand...

I know.

The cut-out relay is nothing more than a magnetic switch. When the battery voltage is less than the output of the generator the relay closes and allows current to flow to the battery. When the charge in the battery exceeds the output of the generator, the relay opens

I'll just throw another fly in the ointment so to speak. The original generators with cut out and high low charge, usually carried a higher field current flow. When you put a voltage regulator on those it will push more current through the voltage regulating points and cause premature failure. As we all well know, the new regulators you get now days are difficult to keep working anyway. Then another thing, it is difficult to actually buy just a cutout now days. Some use a diode in place of the mechanical points, and some use a regulator and only use the cutout portion. For plain and simple, it is hard to beat the high , low charge unless you put in long days of constant running then you will run into over charging.

Good decision JR!

I had a Minnie Mo UTU with a cutout. One of my kids was pushing snow with it a couple winters ago, forget and ran it several hours with charge switch on "high". It ended up exploding a nearly new battery (fortunately he was off the tractor when it let go).

I immediately swapped the cutout with a regulator and put in another new battery. Haven't had a lick of trouble with it since.