F800GS R/R Mosfet replacement....How to...

[WayneC1]

Thanks for posting the info re the Croatian Co, very good info, really appreciated, we have some F650 single owners in that part of the world so have relayed the info over to F650.com as there are VR probs with the single & will see if they are
able to go further with Croatia

On the F800 it is clear from the brilliant work done by Joel, ebrabaek and others that the primary problem is lack of cooling to the stator & that wont be resolved without a design change

The work around if you like is to try to reduce stator temps by a VR change, Increasing the VR regulation voltage using the Shindengen FH12 shunt regulator provides a limited but useful reduction in load on the stator. Going to the series pass VR further reduces the load & hence temperature of the stator

All I can say is I am glad I am only looking for a replacement VR for the single to overcome our limited problems

[ebrabaek]

Originally Posted by Mike.C

Hey Mr Beak, your too popular! Your pic sharing site has blocked em because so many users like em... go figure

I know... I'm sorry..., It will reset tomorrow....and all will be well...... I have had some issues with Photo bucket last time they revamped their site... I lost hundreds of links.... so I stopped paying....and sometimes when projects fly off the wall.....I bust their buffer........ All will be visible...tomorrow.....

Erling

[cathulu]

I suspect your heat sink mount is fine, the mosfet has a low Rds so the i^2r losses are lower than the stock regulator... Your anecdotal observations support that. Joel did not make a distinction between the two.

This is a very interesting thread along with all the others on the stator issue.

Sent from my GT-I9100M using Tapatalk 2

[ebrabaek]

Originally Posted by cathulu

I suspect your heat sink mount is fine, the mosfet has a low Rds so the i^2r losses are lower than the stock regulator... Your anecdotal observations support that. Joel did not make a distinction between the two.

This is a very interesting thread along with all the others on the stator issue.

Sent from my GT-I9100M using Tapatalk 2

Yeppers...... What will be interesting is the temperature before and after the Aluminum bracket.... My gut feeling is that this mosfet R/R unit runs so cool to start with... It does not need the frame cooling.... I was stumpted as of how hot the stock R/R runs.... Really hot...

Erling

[JRWooden]

If the i^2 * R losses are less in the R/R ... might that be actually be a bad thing?

This MOSFET R/R is still a shunt design right?
So if the losses are less in the R/R and the resistance of the stator is unchanged,
then total circuit resistance is lower and the max. current would be higher ... thus creating MORE i^2 * R heating
in the stator due to the higher current....

Or am I AFU here?

[Gangplank]

Originally Posted by JRWooden

If the i^2 * R losses are less in the R/R ... might that be actually be a bad thing?

This MOSFET R/R is still a shunt design right?
So if the losses are less in the R/R and the resistance of the stator is unchanged,
then total circuit resistance is lower and the max. current would be higher ... thus creating MORE i^2 * R heating
in the stator due to the higher current....

Or am I AFU here?

Isn't stator only one way? So higher Max output of RR Means less draw on stator = less heat.

[JRWooden]

Originally Posted by Gangplank

Isn't stator only one way? So higher Max output of RR Means less draw on stator = less heat.

I don't think it's one way but I wouldn't bet more than a 12-pack on it ...

I though the stator was basically just coils of wire tied together in a "Delta" configuration.

Schematically like this picture: http://www.teal.com/products/App%20note%20AN-15.htm

[ebrabaek]

Originally Posted by Gangplank

Isn't stator only one way? So higher Max output of RR Means less draw on stator = less heat.

That's what I understand...... If the R/R has to regulate the voltage down to 13.8 volts by the way of a fancy short....there is more heat dissipated....than if it only regulates down to 14.4......

Erling

[ebrabaek]

Originally Posted by JRWooden

I don't think it's one way but I wouldn't bet more than a 12-pack on it ...

I though the stator was basically just coils of wire tied together in a "Delta" configuration.

Schematically like this picture: http://www.teal.com/products/App%20note%20AN-15.htm

Your correct....

Erling

[JRWooden]

Originally Posted by ebrabaek

That's what I understand...... If the R/R has to regulate the voltage down to 13.8 volts by the way of a fancy short....there is more heat dissipated....than if it only regulates down to 14.4......

Erling

Maybe I don't understand what you mean when you say "one-way" ...

I do agree that regulating at a higher voltage is GOOD
(more voltage means less current ... so good),

but beyond that it seems like in a shunt design system, with our stators especially,
INefficient R/R would be better ...
i.e. a higher resistance path to ground in the R/R would be an advantage in that it would help limit the current flow thru the stator coils when less than full output is required.

[ebrabaek]

Originally Posted by JRWooden

Maybe I don't understand what you mean when you say "one-way" ...

I do agree that regulating at a higher voltage is GOOD
(more voltage means less current ... so good),

but beyond that it seems like in a shunt design system, with our stators especially,
INefficient R/R would be better ...
i.e. a higher resistance path to ground in the R/R would be an advantage in that it would help limit the current flow thru the stator coils when less than full output is required.

Perhaps " one way" is not a good Phrase..... as it really isn't. As you mentioned it is still a shunt....but effectively does a better job shunting the excess power, than the stock R/R. The red lettering is what I'd like to focus on, and it appears that heat dissipated within the mosfet R/R....is less than the stock unit. That does not necessarily mean that more heat is now present in the stator. But someone with more knowledge than me...could perhaps chime in as to the scientific explanation here....

Erling

[JRWooden]

Originally Posted by ebrabaek

Perhaps " one way" is not a good Phrase..... as it really isn't. As you mentioned it is still a shunt....but effectively does a better job shunting the excess power, than the stock R/R. The red lettering is what I'd like to focus on, and it appears that heat dissipated within the mosfet R/R....is less than the stock unit. That does not necessarily mean that more heat is now present in the stator. But someone with more knowledge than me...could perhaps chime in as to the scientific explanation here....

Erling

I am certain the higher voltage is a good thing all around ... the battery is happier, and the stator is happier... win-win.

Without a real set of test cases being run, in which thermocouples are installed in the stator and the various configurations tested... I don't know ........... but thinking about it ... it almost seems like the -SC version of the R/R might be the "local optimum" ............

[14TLC]

Originally Posted by WayneC1

Thanks for posting the info re the Croatian Co, very good info, really appreciated, we have some F650 single owners in that part of the world so have relayed the info over to F650.com as there are VR probs with the single & will see if they are
able to go further with Croatia

Glad I could help. For the F650 single they recommend their serial type R/R, model 14V-3F-15A-A. It costs about 45 eur. I don't know for which production year of F650 is applicable but one can always consult with them when baying one.

[ebrabaek]

Originally Posted by JRWooden

I am certain the higher voltage is a good thing all around ... the battery is happier, and the stator is happier... win-win.

Without a real set of test cases being run, in which thermocouples are installed in the stator and the various configurations tested... I don't know ........... but thinking about it ... it almost seems like the -SC version of the R/R might be the "local optimum" ............

I don't think so..... As the higher voltage should ease the load on the stator.....And...just because the R/R dont get as hot...... does not mean that more heat is going to the stator. But as you duely noticed....No body will know until a lead is placed on the stator. We know the old on eventually will eventually kill the stator..... we also know is kills the battery....fairly fast as well..... This one will/should not kill the battery....so at least one achievement here.....Perhaps two...

Erling

[ebrabaek]

Let me know if there is any interest in a group buy....... I could ask.......as I keep testing the unit.....

Erling