LED headlight anyone?

[George R. Young]

If you take a look at
https://www.vstrom.info/Smf/index.php/topic,20426.0.html
you'll see that the stator current rises with RPM to 27A at about 3000 RPM and then stays constant with a shunt regulator.

With a series regulator, the stator current is around 14A supplying the things that need current, primarily headlight, taillight and ignition.

Twice the current flowing in the stator resistance implies 4 times the heat. So if you want to reduce the heat damage to your stator by a factor of 4, the series regulator does it.

[Ken Williams]

Data presented by George indicates IR power dissipation in the stator for the vstrom with a series regulator is 0.25 of the dissipation with a shunt regulator.  Vision experience should be similar.  This reduction in stator heating should improve stator life.  If I had to replace the stator and regulator on a Vision, I would certainly go with a series regulator. 

[The Prophet of Doom]

You are reading current, but thinking power.  Current should not be confused with heat generation.  It isn't about current, it's about power (more power=more heat) and power is a function of voltage - or more specifically voltage drop.  That voltage drop is caused by resistance. 

With a medium load the series reg's input is disconnected half the time so the meter reads half the current (meters average the reading), but actually it's full current half the time and no current the other half, so it averages as half.  With a shunt regulator it's full current all the time because it's always connected to something, but the resistance varies depending on whether it's shunting or not.
NOT DRAWING - series regulator   power = 0 current  = 0
                      - shunt regulator    power = max current² * 0 resistance = 0
DRAWING        - series regulator   power = max current² * resistance
                      - shunt regulator    power = max current² * resistance

They are exactly the same, even though they operate differently and measure differently on your meters (unless you happen to have a watt meter)  It's largely a marketing ploy though there are other benefits of the series type.  Neither design however is inherently responsible for toasting stators - which is how we got into this discussion in the first place.

The trouble is that blaming reg design stops you from seeking the real cause which is high resistance in the circuits (High resistance = high power = high heat).  That high resistance is a fault condition on your bike which is why some bikes last for 20 years on a stator and others last only a short time.  They all have the same design, they don't all share the same faults.
Aside from poor stator quality which you can't do much about,  My top 3 places to look at are:
1.  The connector to the R/R - these are in a bad place for collecting dirt and oil, and many have different metals on either side which lead to corrosion and resistance.  Remove the connector and solder the wires.
2.  Battery - Don't use your bike as a battery charger.  Keep it on trickle, or charge before you ride
3.  Ignition switch - measure the voltage between your red and brown wires with all the lights off.  It should be close to zero.  If not, then pull apart and clean your ignition switch.

[Rikugun]

Sadly, most of the electrical discussion is above my pay grade. From a practical standpoint, POD's checklist of potential high resistance connections is certainly something everyone is capable of looking into. For me, the ignition switch is the last remaining piece of that puzzle and is therefore on my to-do list.

To Ken's point, if I was faced with replacing the components I'd probably try a series regulator. Why not - I've tried all the rest and after all, it's what the kids are doing these days.  :)

[George R. Young]

. . .With a medium load the series reg's input is disconnected half the time so the meter reads half the current (meters average the reading), but actually it's full current half the time and no current the other half, so it averages as half.  With a shunt regulator it's full current all the time because it's always connected to something, but the resistance varies depending on whether it's shunting or not.
NOT DRAWING - series regulator   power = 0 current  = 0
                      - shunt regulator    power = max current² * 0 resistance = 0
DRAWING        - series regulator   power = max current² * resistance
                      - shunt regulator    power = max current² * resistance

They are exactly the same, even though they operate differently and measure differently on your meters (unless you happen to have a watt meter)  It's largely a marketing ploy though there are other benefits of the series type.  Neither design however is inherently responsible for toasting stators - which is how we got into this discussion in the first place.
. . .

The difference is that the shunt setup is drawing all the time, while the series setup is drawing only some fraction of the time, so the stator  heating is less.

. . .
The trouble is that blaming reg design stops you from seeking the real cause which is high resistance in the circuits (High resistance = high power = high heat).  That high resistance is a fault condition on your bike which is why some bikes last for 20 years on a stator and others last only a short time.  They all have the same design, they don't all share the same faults.
Aside from poor stator quality which you can't do much about,  My top 3 places to look at are:
1.  The connector to the R/R - these are in a bad place for collecting dirt and oil, and many have different metals on either side which lead to corrosion and resistance.  Remove the connector and solder the wires.
2.  Battery - Don't use your bike as a battery charger.  Keep it on trickle, or charge before you ride
3.  Ignition switch - measure the voltage between your red and brown wires with all the lights off.  It should be close to zero.  If not, then pull apart and clean your ignition switch.

Certainly connector with high resistance are a problem, but they cause heating of the connector, not of the stator. The only thing that heats the stator is the current flowing through it, and if a connector has high resistance, it would tend to reduce the current.

[fiat-doctor]

The only thing I know for certain is that we have some VERY smart people on this list!

[Rikugun]

It does make for thought provoking and interesting reading. As smart as they may be however, the discussion is largely academic. Without consensus regarding cause/effect/mitigation, it's all just lofty theory. With all due respect to the participants of course.  :)

[Ken Williams]

Stator wiring has a small but non-zero resistance.  The stator is heated mainly by the current flowing through it.  Stator current is approximately equal if the battery is being charged by this current or it is being shorted through low resistance in the shunt regulator.  The stator is always being heated by this current flow while the engine is running with a shunt regulator. 

With a series regulator stator current is interrupted when the battery requires no help to maintain proper operating voltage.  Therefore, the stator is heated only when current is supplied to the battery.  Unless stator output is always needed to maintain battery charge, the stator should be heated less with a series regulator.  Less power dissipation in the stator leads to a lower temperature and should lead to a longer stator life. 

With either regulator the most power is taken from the engine when supplying current to the battery.  This power is current multiplied by system voltage.  Much less power is taken when a shunt regulator is shorting the output since the phase current is flowing through a small resistance.  This power is approximately the same current multiplied by (.4 volt?).  With a series regulator virtually no power is taken from the engine when not charging the battery. 

When the series regulator shuts off a phase, there is voltage spike in the stator that attempts to maintain the current flow.  The regulator has to have sufficient protection to snub this voltage spike or semiconductors and conceivably the stator could be damaged.  Semiconductors designed specifically for this task have been commonly available for decades.  I assume modern series regulator designs adequately handle switching transients. 

[The Prophet of Doom]

It's all just lofty theory. With all due respect to the participants of course.  :)

Quite so, and I have to admit, that it's all rather parroting what I've read or other people have told me that I make personal sense of.  I'll bet none of us have sat in an auto electrics lab and run the scenarios in a scientific manner.
The only thing I know for absolute certainty is that I've been scrupulous about unwanted resistance (prompted by my RZ meltdown in 1987), and my stator is still a nice honey colour using a stock r/r.


It will stay that way forever unless I get away from my computer and go and re-shape my seat pan.  I'll stop talking about it.

[Rikugun]

Thanks POD, Ken, and George. At least there seems to be consensus the series regulator may have some benefits - or at least that's my take away.

And yes Prophet - for the love of Thor, get that bike back on the road!