Alternator basics

[Clinton Horn]

I would like someone to offer some basic knowlwdge on the XX alternator-R/R.

What I think

1. The alternator appears to produce max output at about 2 thousand RPM.

2. The R/R converts AC current to DC AND regulates the amount of current that is allowed to charge the battery and or power lights fan, pump etc.

3. The amount of current produced by the alternator is subject only to RPM. Load has nothing to do with it. Excess capacity is wasted by grounding the output and producing heat.

What I want to know.

1. If the alternator output is constant, why is a dead battery any harder on the R/R than a fully charged one? Are the diodes "stressed" by doing what they are designed for, ie converting AC to DC? Is the excess energy wasted as heat before or after it is converted to DC? If after, then the Rectifier portion of the device never sees any change (except RPM)

2. As for jump starting a motorcycle with a car. The car battery is much larger and has more ampacity. The current needed to roll the starter is a "demand" made on the battery not like a fire hose in that the system will only consume as much energy as necessary. It appears that some people assume that the jumper cables will allow massive amounts of current to enter the charging loop and fry the system. While I can see the potential, the only caution I can see is to make sure that the polarity is correct and there is no unintentional grounding. Does it matter that I am jumping the system with 10 amps or 100 amps as long as I make the correct connections? Since the borrowed current is already DC, the rectifier portion of the XX should be doing no work at all?

I am trying to learn sound electrical properties not collecting wive's tales or things that a "neighbor told you"

[shovelstrokeed]

There is a distinct danger to the battery if it is really discharged. The high current charge it will receive via the jumper cables can easily overheat the battery and do things like warp plates, boil off electrolyte and in extreme cases maybe even cause the battery to explode.

In addition, a running car's alternator is designed to deliver much higher loads than the motorcycle battery can withstand and the battery will be again subjected to too high a load.

As far as I know, the regulator measures the DC current on its output and does ground inputs. However, it may well be that it will 'see' the inrush current to the discharged battery and attempt to regulate that, again causing overheating and possible damage to the component.

I have not, nor do I have any intention of doing so, tested this for myself. You, of course, are free to do so if you wish.

[gharknes]

I would like someone to offer some basic knowlwdge on the XX alternator-R/R.

What I think

1. The alternator appears to produce max output at about 2 thousand RPM.

yup about right

2. The R/R converts AC current to DC AND regulates the amount of current that is allowed to charge the battery and or power lights fan, pump etc.

....sort of..........it is the voltage that is regulated, if voltage from alternator is above battery voltage then the battery will charge, the limitation is how much current can be provided as load increases, this all equals power

3. The amount of current produced by the alternator is subject only to RPM. Load has nothing to do with it. Excess capacity is wasted by grounding the output and producing heat.

....current is limitless until something breaks down...a bit like the function of a fuse, anything in the charging circuit could be defined as a fuse, the regulator controls the voltage which in turn controls power which is almost like a variable fuse, if voltage drops then current will increase to supply the same power then something gives.

What I want to know.

1. If the alternator output is constant, why is a dead battery any harder on the R/R than a fully charged one?.............it isn't, a dead battery as you mention is faulty and creates a greater drain on the charging circuit

Are the diodes "stressed" by doing what they are designed for,

....technically ...yes, adding load to the charging circuit relieves the work load on the rectifier circuit, not the diodes as such.

2. As for jump starting a motorcycle with a car. The car battery is much larger and has more ampacity. The current needed to roll the starter is a "demand" made on the battery not like a fire hose in that the system will only consume as much energy as necessary. It appears that some people assume that the jumper cables will allow massive amounts of current to enter the charging loop and fry the system.

..do they ?

While I can see the potential, the only caution I can see is to make sure that the polarity is correct and there is no unintentional grounding. Does it matter that I am jumping the system with 10 amps or 100 amps as long as I make the correct connections?

..current is a product - voltage is the force, so yes

Since the borrowed current is already DC, the rectifier portion of the XX should be doing no work at all?

...if you load the charging circuit to its full capacity the the regulator not rectifier will be relieved of it duties

think of electricty like a river, the volume of (depth width) water is the current, the voltage is the incline.