Generator Electricity

[treeguy]

I have a question thats been bugging me, but may sound so dumb that I can't wait to see the response. Whether you are operating a car, deuce, boat, or tractor everyone know that you never disconnect any battery cable with the engine running. This is because the electricty generated by the altinator has no where to go if you are not using it for accessories. So my question is: when you have your beloved genny up and running but don't have anything connected to it to run, what happens to the electricity being generated. Its there right, all the time she's running, you can instantly get power from the convenience plug, so why doesn't it build up and fry itself? Any ideas about this electrical magic?

 

[Westech]

Voltage regulator. You can take off the charging wire from a alternator and be ok.. the VOLTAGE REGULATOR controls the out put.. no load, no out put.... The gen set is not making full power all the time....

you seam very confused on a lot of things the week. Everything ok?

 

[Blood_of_Tyrants]

The generator doesn't generate any power unless it is connected to a power consuming device. Just like a battery doesn't start it's chemical reaction that generates a current until you close the circuit.

BTW, an old way of checking if your alternator is working is to disconnect the battery ground. If your alternator is bad the engine will die.

 

[treeguy]

Westech, I got a kick out of that one! I haven't been able to spend a lot of time on S.S. in a while and now my girlfriend is away so I have time to ask dumb questions that have been bugging me. The other (problem) is that there are so many great posts to read it makes my brain hurt, then I second guess (like the oil) if I'm doing things right. (perfectionist)!

 

[PeterD]

Easy to explain why not to disconnect an (alternator usually) from a running engine. Generally the alternator is putting out a given voltage for the current load. Disconnecting the battery can cause a momentary surge in the alternator's output, which eventually the regulator will correct for but that takes some time.

OK, you say, why doesn't this happen when I use my lights or other things in the car... Easy: the battery serves as a filter to keep surges down to a minimum. In theory you can put a big capacitor across the main power (battery) lines and then disconnect the battery--but that's not either easy to implement nor absolutely going to protect things.

So think of your battery as being like a giant surge suppressor, and you are going to be close to what is happening.

(BTW, what blows when you disconnect a battery like this (running) can be almost anything but commonly it is the regulator, diodes in the alternator, or any computer (such as a vehicle's ECM/PCM/TCM/BCM).

 

[stampy]

That is also why you have to be careful jumping a car that has a computer, and another the reason I like the old iron.

 

[treeguy]

Thanks for the explanation. The voltage regulator was the key, I thought generators would keep on producing electricity but didn't know where it went if nothing was attached to it. A battery in a vehicle; just like I thought; a pooling area for unused power, thats why disconnecting it would be bad while running. Thanks again!

 

[shovelheadmike]

All things being equal, a generator will put out voltage proportional to the speed at which it is turning. The faster it turns, the higher the voltage. This is where the voltage regulator comes in. It you open the circuit, left to its own, a generator will go to max voltage. However, regardless of the terminal voltage, if it is an open circuit, there is no current flow. So, no actual power is being produced--just voltage potential. The definition of power in watts is the voltage times the current. Once you close the circuit, the more load you put on it lowers the electrical resistance which increases the current draw and the generator is.called upon to produce more.power.

 

[PsycoBob]

On a deuce, you can either flip the master switch, or unplug the short wire from the alternator- it's the one that powers the regulator. It's different from the one that senses voltage. M-series don't normally have separate output/sense wires. Much safer than stress-testing the regulator/rectifier assembly with 200v+ spikes.

On automotive systems, a similar little wire is used to power the alt only when the engine is running, not when cranking or stopped.

Plug in a voltmeter direct to the batteries, and turn off the master switch in a deuce. Voltage droops- switch on, alt makes power again and voltage goes back up. Fast alternator test. You can even use the brightness of the lights, rather than a voltmeter.

 

[DLJ]

This reminds me of an old farmer years ago was so mad at the power company he went out to the barn unscrewed all the bulbs ,turned the lights on and let all there power run out on the floor.

 

[treeguy]

I bet the farmer was shocked when he didn't have a big mess on the floor to clean up!

 

[shovelheadmike]

Years ago, I used to work at a power station. When people learned of this, they would always ask if I got free electricity. My answer was always yes, I did receive free electricity--I got all that I could carry home in a 5 gallon plastic bucket.

 

[treeguy]

 

[Isaac-1]

This reminds me of an old farmer years ago was so mad at the power company he went out to the barn unscrewed all the bulbs ,turned the lights on and let all there power run out on the floor.

I have a relative that once had a dealership mechanic tell them the reason the battery kept running down on their van was the bulb on the dome light was burned out and letting the elecricity run out.

Ike

p.s. no one ever did track down the source of that power drain (it would run the battery down if not started every couple of days)