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Old 04-14-2012, 06:29 PM   #59
JoelWisman
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Joined: Apr 2009
Location: STL, MO, USA
Oddometer: 1,392
Back amongst the dead after 4,000 miles, 50% off road and the creation of so venison along the way :)

1: The stator and stator cover temperature are almost totally disconnected. The stator has perhaps 5% surface connection. Iron to aluminum with varnish between.

Net result, with thermocouples glued to stator windings, running a garden hose on the stator cover full blast did not detectable cool the stator. Using a heat gun to warm the center of the cover up to 350 degrees seemed to heat the stator windings 5 degrees after 5 minutes, but thats so small that I can't be sure heating the cover caused it.

If you want meaningful readings, you need to glue thermocouples to the winding and test the bike with each R/R in exactly the same ambient and wind speed.

2: The article linked above about Mosfet V SCR, almost every single thing in it is wrong. It sounds good and would make sense if it were true, but it is not. SCR R/Rs are always more reliable if the components are spec'd the same.

Electrical components do age faster when hotter, but most stock SCR regulators, and particularly the ones BMW uses will last the lifetime of the bike.

SCR regulators do NOT become less accurate with aging, in fact, the components for sensing voltage are precisely the same with both types of shunt regulator only the mosfet type needs additional components to get the voltage to the switching gate up higher and this is a common cause of failure which an SCR based regulator does not even have.

Immaterial because the particular Mosfet regulator I recommended is robust with a hugely oversized FET and is just as reliable as the stock, but I can't read an article that flawed, or sit back while thousands read MOSFET cool-aid and not chime in.

Mosfet regulators produce more precise regulation out of the box because they are faster. This does not vary with age with the mosfet or SCR style. Mosfet regulators also run cooler so if it is mounted in a place that burns you, a FET is better.

Mosfets are more efficient at passing power, but in our application, when passing power they are deliberately wasting it, so FET regulators are no more efficient at passing charging current to the bike and battery. The rest of the components in both R/Rs are exactly the same, except for some additional components that the FET regulator needs for switching the FET gate which produces a measurable but tiny loss.

I linked to the particular Mosfet regulator because and only because I know it to be regulated where we want voltage to be AND because I know that particular unit to be reliable.

There is ABSOLUTELY NO across the board benefits from Mosfet versus SCR regulators other then tighter out of the box regulation and less heat if the regulator is mounted in a place that heat matters.

Mosfet for those in the electronics field stands for "Magically Obliterated Smoke and Fire Emitting Diode". SCR stands for "Super Cheap and Reliable".

Once again, the Mosfet R/R used in this mod IS robust and reliable, but this is absolutely not the case across the board for regulators.

Ok, blood pressure down slightly after typing that.

Yes ebrabaek, the doubled output wires are in parallel, and the shutdown current drain sequence you measured is normal across the entire K7X platform. Whats fun is on rare occasion, the ZFE hangs a a stage previous to final and drains the shit out of your battery :) It is rare in the latest ZFE firmware load, but still happens.

Outstanding thread my friend, though the all the pictures overran my buffer till I cleaned it

I don't know just how much this will cool the stator, but everything in me says "at least a little". Regulating at a higher voltage there will be more back EMF which will reduce current a little while keeping power about the same or even a little higher. Haven't tested it, but it really seems to me it HAS to cool the darn thing at least a little.

P.S. the stock regulator absolutely does use the frame as a heat sink with a very noticeable temperature rise of that area of the frame. Of the stock R/Rs I have seen fail, the R/R being loose or moved and zip tied were responsible for all but one failure. FYI whoever in the thread said it, I used heat sink grease as well when mounting my R/R :)

If you run the stock JRWooden is right for at least the stock regulator. I have seen one fried in the shop just from running a bike with it unbolted from the frame and it only took 15 minutes though it was a very hot day.

Mosfets can't take as much heat, so I am a little concerned that that carbon fiber bracket MAY cause rapid aging and early failure. Then again, that particular FET regulator is over built and robust and may take it for the life of the bike.
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JoelWisman screwed with this post 04-14-2012 at 06:36 PM
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