Alternator Voltage Sensing

[GoneDiving]

How does an alternator with B+, B-, W, L terminals and internal regulation sense battery voltage? Does the L terminal only provide on/off excitation or does it provide sensing to increase or decrease output as required too?

Thanks

 

[C lectric]

--B+ is the alternator current output to the batteries or loads
--B- is the alternator ground. Many are grounded through the case and mounting BUT best is the direct ground to the B- terminal. Some external regulators require an actual at the alternator ground so this would be the place for that also.
--W is a tachometer signal.
--L is the exciter circuit to give the alternator a kick to start producing voltage which can be under some circumstances a problem at low or idle revs. Often done through a warning lamp.
--S is the sense wire that can when available be lead to the battery + which over rides the internal sensing function. Usually set up so if the S fails the internal regulator will pick up the sense function.
--F is the field which you are unlikely to find on any modern alternator. THis would go to an external regulator.

NOt all alternators have all of these connections.


I have attached a good explanation I just found. There are lots of others. If there are other terminal designations you find simply google them as there are LOTS of these postings available for us to peruse.

http://www.autoshop101.com/forms/alt_bwoh.pdf

 

[Rufus]

This reminds of a question. Our boat originally had 2 Delco 10SI alternators 55 amp...one on each engine. I reconfigured the batteries from two 8Ds to a 6 6-volt golf cart house bank, and a pair of 12V hi amp start batteries. One of the 10SI alternators charged the start batteries. A small case 130 amp Ample Power marine alternator charged the house bank via a smart (Xantrex) external regulator. Last year this alternator failed and I can't get parts (so I'm told).

Here's the question...I have a good automotive Delco 17SI (120 amp with an internal regulator), which fits the available space/bracket. I'd like to utilize the Xantrex external regulator. Is it possible to remove/bypass the internal regulator on the Delco? (I can't find a "how to"). If so, what wire goes where? If not, do I have to worry about the internally regulated 17SI doing damage to the battery bank or to itself? I'm not particularly concerned about spark protection with diesels...should I be?

Thanks (I guess that was more than one question....

 

[GoneDiving]

--B+ is the alternator current output to the batteries or loads
--B- is the alternator ground. Many are grounded through the case and mounting BUT best is the direct ground to the B- terminal. Some external regulators require an actual at the alternator ground so this would be the place for that also.
--W is a tachometer signal.
--L is the exciter circuit to give the alternator a kick to start producing voltage which can be under some circumstances a problem at low or idle revs. Often done through a warning lamp.
--S is the sense wire that can when available be lead to the battery + which over rides the internal sensing function. Usually set up so if the S fails the internal regulator will pick up the sense function.
--F is the field which you are unlikely to find on any modern alternator. THis would go to an external regulator.

NOt all alternators have all of these connections.


I have attached a good explanation I just found. There are lots of others. If there are other terminal designations you find simply google them as there are LOTS of these postings available for us to peruse.

http://www.autoshop101.com/forms/alt_bwoh.pdf

Many Thanks. Both your explaination and the doc are very informative.

 

[C lectric]

I have modified my own alternators to work with an external regulator, a 22SI and now a 24SI. I have kicked myself for not going with the 28SI but it is done now.

If you are not comfortable with doing the same then take the alternator you wish to modify for external regulation to a shop that rebuilds alternators and engine starters. I did not find it hard but I had to study them a bit to decide how to deal with them.



In fact take your failed Ample Power alternator to the shop and ask them.
A good shop may recognize the base alternator A.P. modified.

Just for grins I too have an Ample power regulator, now getting old. My original alternator was the 10DN now long out of use although aboard for an emergency spare., very similar to your old one.

 

[GoneDiving]

Here's the question...I have a good automotive Delco 17SI (120 amp with an internal regulator), which fits the available space/bracket. I'd like to utilize the Xantrex external regulator. Is it possible to remove/bypass the internal regulator on the Delco? (I can't find a "how to"). If so, what wire goes where? If not, do I have to worry about the internally regulated 17SI doing damage to the battery bank or to itself? I'm not particularly concerned about spark protection with diesels...should I be?

Thanks (I guess that was more than one question....

I've got a similar aim. I'm putting in a monster house bank and would like to be able to throttle the alt's output current if the bank is low to prevent long runs at full rated current.

There is lots online about boosting output (for audio heads) but little on throttling. Shouldn't be too hard to implement without changing everything ?

 

[Cigatoo]

--B+ is the alternator current output to the batteries or loads
--B- is the alternator ground. Many are grounded through the case and mounting BUT best is the direct ground to the B- terminal. Some external regulators require an actual at the alternator ground so this would be the place for that also.
--W is a tachometer signal.
--L is the exciter circuit to give the alternator a kick to start producing voltage which can be under some circumstances a problem at low or idle revs. Often done through a warning lamp.
--S is the sense wire that can when available be lead to the battery + which over rides the internal sensing function. Usually set up so if the S fails the internal regulator will pick up the sense function.
--F is the field which you are unlikely to find on any modern alternator. THis would go to an external regulator.

NOt all alternators have all of these connections.


I have attached a good explanation I just found. There are lots of others. If there are other terminal designations you find simply google them as there are LOTS of these postings available for us to peruse.

http://www.autoshop101.com/forms/alt_bwoh.pdf

That’s a nice explanation / article. Thanks for sharing.

 

[Iggy]

--B+ is the alternator current output to the batteries or loads
--B- is the alternator ground. Many are grounded through the case and mounting BUT best is the direct ground to the B- terminal. Some external regulators require an actual at the alternator ground so this would be the place for that also.
--W is a tachometer signal.
--L is the exciter circuit to give the alternator a kick to start producing voltage which can be under some circumstances a problem at low or idle revs. Often done through a warning lamp.
--S is the sense wire that can when available be lead to the battery + which over rides the internal sensing function. Usually set up so if the S fails the internal regulator will pick up the sense function.
--F is the field which you are unlikely to find on any modern alternator. THis would go to an external regulator.

NOt all alternators have all of these connections.


I have attached a good explanation I just found. There are lots of others. If there are other terminal designations you find simply google them as there are LOTS of these postings available for us to peruse.

http://www.autoshop101.com/forms/alt_bwoh.pdf

A great PDF! I knew that the Alt made AC current but I never knew that there were three AC sine waves. So the bridge is seeing a more steady voltage. So, no caps are really needed. Interesting...............

 

[C lectric]

The actual output from the alternator is an AC sine wave similar in form to what is used in industrial applications. Our alternators use the diode bridge to turn it into a pulsating DC voltage. THe three sine waves provide a far steadier voltage since the pulses fill in the gaps left by the previous pulses.

If you look at the DC voltage using an oscilloscope you will see the pulses.

In our boat systems with batteries the batteries tend to smooth out those pulses even more acting like a capacitor. The pulses won't disappear entirely but enough so that without a scope neither you nor your equipment will be bothered by the remaining pulses.

 

[C lectric]

I've got a similar aim. I'm putting in a monster house bank and would like to be able to throttle the alt's output current if the bank is low to prevent long runs at full rated current.

There is lots online about boosting output (for audio heads) but little on throttling. Shouldn't be too hard to implement without changing everything ?

That can be done. There are external regulators that can use a temperature sensor which is exactly intended for that purpose. Balmar, Wakespeed, are two. They must be programmed for that function but it can be done.

Of course your alternator MUST be capable of being controlled by an external regulator. You can purchase alternators already modified or take yours in to be modified.

I can think of other ways of doing this butone way or another the alternator MUST be modified.

 

[GoneDiving]

I can think of other ways of doing this butone way or another the alternator MUST be modified.

Thanks again. I need to confirm what terminals are available externally and internally but yes, modifying for an external regulator seems the best option. It's definitely internally regulated now

Just for clarity, does removing power to the L or ACC terminals, but having the alternator continue to turn, stop the output or damage the alternator?

 

[C lectric]

No, if the alternator is spinning and the internal regulator has not been disabled or removed the alternator will continue to produce voltage and current as before.