Alternator Voltage Regulator Output Level

Dr.Jeff

Dr.Jeff

True Classic
In the "what you did today" section, Karl mentioned his new replacement voltage regulator did not have the same output as the old one. Here was my reply:

Karl, I'm assuming you have the Bosch alternator. As you know, the regulators for them are a very common part that fits a ton of their units for countless vehicles over decades of production. I've found the same, the regulator output does vary a bit from one to the next. I think it has to do with production variances; they are produced at numerous plants all around the world, and naturally there are many different (non Bosch) makers of them as well. There is a method of making the output level "adjustable" with a mod. I've never tried it and frankly I'm not even sure if it is a legitimate mod; not being a electronics expert I really can't say, but it sort of seems a bit questionable to me. Here is a discussion about it from the VW community (sorry, it has the usual Vortex rambling):
https://forums.vwvortex.com/showthread.php?4308948-Re-volting-idea-for-regulators.

And here is a Volvo specialist that offers them premade:
https://www.240turbo.com/AdjustableVoltage.html

I decided to start a thread about this because I'd like to here what some of our electrical pros have to say about it. The concept sounds great, but the design of it seems questionable to me. However I do not know enough about this to really say.

Inputs?
 
It is all a matter of setting the reference voltage to what you want. However, I'd look for problems elsewhere in the system first to see if anything else is causing the low voltage output. My guess would be too much series resistance some place. One way to reduce the effects of series resistance on battery charging is to use a separate "sense" line for the regulator to sample the battery voltage. Since very little current is in the sense line, series resistance has very little effect. That will solve the battery voltage problem but would not improve the series resistance issue for electrical loads other than to have more battery voltage to work with. The circuit itself is pretty simple. The alternator output is compared against the reference. If it is too low, it increases the field current until the right voltage is reached. If the voltage is too high, it reduces the field current. I can't think of a good reason why the reference voltage would not be set at the factory in the correct range for a 12V (really ~13.6) lead acid battery. Of course, the old mechanical regulators could be adjusted by turning a screw that would change the duty cycle of the vibrating contacts that controlled the field current.
 
I haven’t checked mine for actual operation, just on my gauge the position of the needle is lower. My car has always shown higher voltage so perhaps it has been an example of the VR actually having been going bad for a long time.

Agreed one should ensure the rest of the system is up to snuff, throwing more voltage into a poorly conducting set of connections is a bad call. The Volvo seller of parts makes this clear in his write up.

The reality is that all voltage regulators will be subtly different and deliver different voltages from different alternators. The stack up of manufacturing variation and wear over time conspire to drop the voltage to the battery and the system. Tuning the regulator to produce what is actual spec once assembled would be the big value to having the adjustable unit, not to overcharge but to get to the correct minimum spec.

The price is just a few dollars more then a the open line standard type as well:
B6C911D0-C8E2-4A43-A8C5-BA4359B92B4F.jpeg
 
I'm wondering if the 'pre-made' adjustable one has basically the same mod as was described in the VW article; some sort of diode added to the ground wire for the regulator? To be adjustable it must not be a fixed diode, but is there a similar electrical component that does the same effect with the ability to be varied? Or would the "adjustable" version have a completely different design, taking a different approach to setting the voltage output?

For that matter how does adding a diode change the voltage reference? I thought diodes were just "one way" valves? Seems like you would need a resistor rather than a diode? Or am I completely mixing up my extremely limited knowledge of electronics? Thanks in advance for a very basic explanation that even I can understand. :oops:
 
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kmead said:
The price is just a few dollars more then a the open line standard type as well
Click to expand...
I suppose that depends. These are listed at $32. I typically pay about $8 for a new regulator, but yes - they usually retail closer to about $25. Still not a bad price for having the ability to fine tune things. Assuming they are a legit thing; although these ones (from the Volvo specialist) have been available for a few years, aside from them I've never heard of this in all the years of doing this stuff. Kind of makes me wonder.

Not so much to try and overcome a problem, I'm especially considering something like this for use with a aftermarket stand alone ECU where proper voltage level is rather critical. You could measure the voltage going into the ECU and adjust the regulator accordingly.
 
Dr.Jeff said:
I'm wondering if the 'pre-made' adjustable one has basically the same mod as was described in the VW article; some sort of diode added to the ground wire for the regulator? To be adjustable it must not be a fixed diode, but is there a similar electrical component that does the same effect with the ability to be varied? Or would the "adjustable" version have a completely different design, taking a different approach to setting the voltage output?

For that matter how does adding a diode change the voltage reference? I thought diodes were just "one way" valves? Seems like you would need a resistor rather than a diode? Or am I completely mixing up my extremely limited knowledge of electronics? Thanks in advance for a very basic explanation that even I can understand. :oops:
Click to expand...

Diodes are a one way valve but when they are conducting there is a voltage drop across the diode. Typically for a silicon diode it's 0.7V so by adding a diode in the sense line you are making the battery voltage look 0.7 volts lower than it actually is causing the voltage regulator to raise the output by 0.7V to compensate. If you want to get fancy you could use an op amp configured as a voltage follower with a variable resistor in the feedback to make an adjustable voltage drop to do in the sense line. I did this years ago to adjust the voltage on rally cars to max out the lights, we found 15.5V didn't bother the electrical system of the car at all but it made the lights work great. I don't think I would try that on a new computer controlled car.
 
bpimm said:
If you want to get fancy you could use an op amp configured as a voltage follower with a variable resistor in the feedback to make an adjustable voltage drop to do in the sense line.
Click to expand...
Thanks Brian. Do you suppose the adjustable one from the Volvo supplier has something like you described in it, or something even simpler? I only ask that because what you described sounds like it might not fit inside a normal regulator like theirs does. Although I really don't know what a "op amp with a variable resistor" looks like, so maybe it would fit.
 
fiatfactory said:
Here's a link to a thread about voltage regulators from back in 2015
Click to expand...
Thanks. I did not see anything in it about adjustable regulators, but there was mention of some that have a slightly higher output. However all of the ones discussed there are external units compared to the internal ones discussed here. And it would be a bit difficult to convert from internal to external because the regulator is also the brush pack on these Bosch units.
 
well it got me thinking the RE56 with the external link that you "cut" to get the extra voltage... that would be the perfect spot to bridge with an "op amp with a variable resistor" (which I think must be some sort of variable resistance pot) seems to me the maker of the volvo bits might be doing something similar.

SteveC
 
Dr.Jeff said:
Ahhh, now I'm with you. That cuttable link with two voltage settings is a rather peculiar set up. Makes me curious what it was intended for.
Click to expand...
Sometimes you just need that extra push over the cliff. The cuttable link must set it to 11.
 
Dr.Jeff said:
Thanks Brian. Do you suppose the adjustable one from the Volvo supplier has something like you described in it, or something even simpler? I only ask that because what you described sounds like it might not fit inside a normal regulator like theirs does. Although I really don't know what a "op amp with a variable resistor" looks like, so maybe it would fit.
Click to expand...

It would fit with today's technology they are tiny..
 
bpimm said:
they are tiny..
Click to expand...
So I Googled it to see just what they are. Saw this:
https://en.wikipedia.org/wiki/Operational_amplifier
Began reviewing it, then after I awoke from my coma, I realized I don't have a clue what it's talking about.

IC-741-Op-Amp.jpg


I get the concept though. And if indeed they are tiny, then I suppose it could be designed into the normal regulator's housing. On the adjustable regulators referenced earlier, there is a small screw poking through the face to make the adjustment. Otherwise they appear completely standard:

B6C911D0-C8E2-4A43-A8C5-BA4359B92B4F.jpg


I'm sure these were designed and made this way from the part manufacturer, and not a aftermarket modification. So I'm guessing they are likely a standard part for some obscure application that uses Bosch alternators (perhaps on some sort of industrial equipment or such). If that is true then I would have confidence in using one. The other reference from the VW forum, to modify a standard one by adding an external component, does not inspire that confidence. Plus it isn't adjustable.

I agree with Karl, it might be worth a look. As Jim said, then you can crank it up to 11 (I remember those amplifiers with a volume dial to "11"). Worst case scenario, you end up adjusting it back to where your stock one was - no harm done.
 
Jeff, the "acceptable battery voltage" I've always heard is 13.2V to 14.8V for a charging system so you have a pretty big window. I'm sure when the regulators are checked during testing if they are in the window they are good. There are many things in the manufacturing process that could have batch at one end of the scale or the other, If you are interested in tweeking it to the upper end of the scale that is easy with the diode trick and works well, if you're high and want to bring it down, that's another story.

The op amp is just a stack of transistors configured to give the user the ability to create many different types of amplifiers out of the simple package. The voltage follower is what's known as a unity gain amplifier meaning the output voltage will be the same as the input voltage, by fudging the feedback just a tiny bit we can get the output voltage to be either a bit higher or lower than the input voltage and in this case that is fudging the feedback to the alternator causing it's output to change accordingly. The adjustable version you show above is just a variable feedback regulator, probably has several op amps in it.

I have ran several versions of voltage "hacks" through the years and had no problems with them, Mainly for maximizing headlight output, you would be surprised how much difference there is in good lights between 13.2V and 14.8V.
 
Dr.Jeff said:
In the "what you did today" section, Karl mentioned his new replacement voltage regulator did not have the same output as the old one. Here was my reply:

Karl, I'm assuming you have the Bosch alternator. As you know, the regulators for them are a very common part that fits a ton of their units for countless vehicles over decades of production. I've found the same, the regulator output does vary a bit from one to the next. I think it has to do with production variances; they are produced at numerous plants all around the world, and naturally there are many different (non Bosch) makers of them as well. There is a method of making the output level "adjustable" with a mod. I've never tried it and frankly I'm not even sure if it is a legitimate mod; not being a electronics expert I really can't say, but it sort of seems a bit questionable to me. Here is a discussion about it from the VW community (sorry, it has the usual Vortex rambling):
https://forums.vwvortex.com/showthread.php?4308948-Re-volting-idea-for-regulators.

And here is a Volvo specialist that offers them premade:
https://www.240turbo.com/AdjustableVoltage.html

I decided to start a thread about this because I'd like to here what some of our electrical pros have to say about it. The concept sounds great, but the design of it seems questionable to me. However I do not know enough about this to really say.

Inputs?
Click to expand...

Hi Jeff,

If you are running an external regulator then you can easily swap in a unit like this one:

https://www.rakuten.de/produkt/regl...ENF_xuNS_G1ZWiuoPyvbZ7yAAdnUnzIYaAt7uEALw_wcB

Also see: https://www.ebay.de/itm/Oldtimer-Re...400816?hash=item3f663099f0:g:tFkAAOSwiiJdAlG0

Cheers,
Dom.
 
bpimm said:
if you're high and want to bring it down, that's another story.
Click to expand...
Can't imagine ever wanting to bring down a good high.

But seriously, thanks for the info. I have a couple of spare used regulators. Just for fun I might experiment with the diode trick, so long as there is no real risk of damaging the alternator ???. I have to go back and re-read that reference for the details. Will selecting a different diode (value?) to use for this create different amounts of an increase? And is it possible to estimate how much increase you would get to determine what diode to use? Or does it not work that way?
 
dcioccarelli said:
If you are running an external regulator then you can easily swap in a unit like this one
Click to expand...
Thanks Dom. I am not using an external regulator, but appreciate seeing the examples of adjustable ones. Steve mentioned them as a comparison for one that has different voltage outputs available, just as an example. The Bosch alt's have a neat internal reg that is also the brush pack. It is very easy to replace and not that expensive, plus requires no external wires, so I like it. These alts seem to be very robust and last forever, with only the need to replace this reg unit after a LOT of miles on them. That is one of the neat features of these adjustable regs, they are a direct replacement for the stock reg. Out of general interest I'd like to discover more about their original intended applications and uses.

I guess having an adjustable reg isn't all that new after reading everyone's comments seeing the links. But I had never seen them available for cars until a couple years ago (when I came across the references I gave). Pretty much all of my vehicles happen to have Bosch alts so these units in particular caught my attention. However I did not think they were a valid thing to use for some reason; it just seemed like another one of those gimmicks that would likely damage your alt. But you guys have given me more info on it and I am changing my impression...thanks to everyone.
 
Dr.Jeff said:
Can't imagine ever wanting to bring down a good high.

But seriously, thanks for the info. I have a couple of spare used regulators. Just for fun I might experiment with the diode trick, so long as there is no real risk of damaging the alternator ???. I have to go back and re-read that reference for the details. Will selecting a different diode (value?) to use for this create different amounts of an increase? And is it possible to estimate how much increase you would get to determine what diode to use? Or does it not work that way?
Click to expand...

All silicon diodes will be about .7V you can stack 2 to get 1.4V and so on.
 
bpimm said:
All silicon diodes will be about .7V you can stack 2 to get 1.4V and so on.
Click to expand...
So now you've open the can of worms. :) Is there a better electronic component that can be spliced into the ground wire (same as with the diode) that comes in different values, allowing a selection of different increases depending on the value chosen? For example something like resistors (not saying that will work, only using them to illustrate). The idea being you can determine how much voltage increase you want and calculate what value of component to insert into the ground.
 
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