Can someone give me a quick tutorial on what the cutout does. I have always assumed that, just based on the name, the cutout stops the generator from generating electricity after the battery has been fully charged, then allows enough electricity through, periodically to trickle charge the battery as the car depletes the battery as it is operating the various electrical systems (ignition, starter, lights, horn, etc).
1. What happens to the electricity generated by the generator when the cutout is actuated and no longer allows the electricity to the battery?
2. What are the symptoms of a bad cutout? Does it go bad gradually, or all of a sudden?
3. What is the difference between the old type cutout and the new Funprojects cutout?
4. What can happen if the generator is allowed to run with a bad cutout?
Jim, your first description is more along the lines of a VR. When the generator runs and creates enough juice, the cutout closes and connects the battery to the generator. It stays that way until the generator is stopped. (As long as it works correctly).
Bad cutout = open line to battery and runaway generator = destroyed generator.
Stuck cutout = destroyed battery from being connected after the car has been shut off.
Jim said: "I have always assumed that, just based on the name, the cutout stops the generator from generating electricity after the battery has been fully charged, then allows enough electricity through, periodically to trickle charge the battery as the car depletes the battery as it is operating the various electrical systems (ignition, starter, lights, horn, etc)."
No, the cutout does not control how much the generator puts out. That is generally controlled by the third brush in the generator.
Question 1.See above.
Question 2.Cutouts are generally bad one of two ways. Either they don't close (they don't allow the current from the generator to go to the battery), or are stuck closed (allow the battery current to feed back to the generator when the motor is off). The symptoms in the first case are a non-charging system (no ammeter deflection). Plus, there will likely be damage to the generator as it will produce current, but will be unable to dissipate the power externally. As such it will dissipate it internally, usually damaging the field windings.
There are no symptoms in the second case until the motor is stopped, at which point the ammeter will show a large negative deflection and the wire to the generator will get hot. At this point the generator becomes a motor and is effectively trying to turn the engine over. It hasn't enough power of course, so the wires get hot and eventually the battery dies, if something else worse doesn't happen.
3. The new Fun Projects device is an actual voltage regulator.
4. See two above.
There's not a lot of difference between a DC motor and a DC generator. When your engine is running, you want the generator to charge the battery, so they have to be connected to one another. However, when you shut the engine down, the battery would try to run the generator just like it was a motor. Since the generator can't turn when the engine is off (Geared tot he camshaft), it would sit there and get hot as it tried to turn but couldn't. This would run the battery down and probably wouldn't do the generator any good either. In steps the cut-out. The cut out will connect the generator to the battery when the generator is 'genning', but disconnect the battery from the generator when the generator is not 'genning'.
The original style did this with a set of electromagnetically operated contacts. Newer ones are just a diode which acts like a check valve. It allows current to flow one direction but not the other.
In an original cutout, there are two coils that will work on the contacts. The contacts, when closed will connect the generator to the battery, through the wiring. When the engine is not running the coils are not energized and the contacts are open, disconnecting the battery from the generator. If the contacts would not open the battery would try and run the generator as a motor and become discharged and heat up the generator. When the engine starts, and the generator begins to build up voltage, the voltage coil will pull the contacts closed, allowing the generator to charge the battery. Then as current is flowing into the battery, the current coil will add pull to the contacts, ensuring that they are closed. Then as the engine slows to minimum or when the engine is switched off, the generator output goes to zero and the battery will start to push current into the generator (backwards). The current coil senses this back flow of current and will cancel the voltage coil pull, hence opening the contacts, isolating the generator from the battery.
The cutout works when the engine starts and stops. Failures that I have seen are welded contacts and failed coil connections.
The regulators of the 1950's and 60's also had a cutout relay, along with a vibrating voltage and current regulators. The cutout in these are basically the same as the model T cutout.
If the car has a bad cutout, it depends on how the cut out failed. If the contacts are welded closed, the battery will discharge and there could be generator damage. If the contacts are burnt off, the generator will always be isolated from the battery and the battery will over time discharge from the normal cars electrical usage. If the either coil connections are bad, you may have intermittent generator charging or no generation action at all.
Cutouts can cause some headaches. You would be better served with a diode cutout, although they have some troubles. A real voltage regulator is probably the best solution, I have a fun projects regulator. The FP regulator will regulate voltage so that the battery will not be over charged (as with a cutout) and this regulator will also limit generator output current which will protect the generator from overheating. Hope this is understandable and helpful.
There's a helpful interactive generator animation at this website. Click on the throttle lever to increase rpm. Click again to increase rpm even more and then you have to click on the RESUME button that appears just above the controls to see the cutout close.
There's also an interactive animation on the Model T transmission on the same website: