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Old 03-25-2012, 07:40 AM   #62
Beastly Adventurer
Joined: Jul 2008
Location: The great state of confusion
Oddometer: 4,315
Originally Posted by JoelWisman View Post
1) would have expected the highest temperature from the pole pieces closest to the header if it was a major influence, but it certainly can't hurt, the stator at least. Time will tell what the header and CAT think of it.

2) Unknown. It will reduce the heck out of stator temp anytime your battery and equipment are not pulling full load. Will it cause electrical interference with other items? Resonate or over voltage the stator insulation? Probably not, but I don't know for certain.

3) Yes! It's impossible for me to calculate. I lack the mathematics and even with them, things of this complexity require full scale testing to quantify. You have inductive reactance, capacitive reactance, eddy currents, magnetic saturation, and resistance, thermal conduction, convection, and radiation just to name the major players. My slightly educated guess is it might drop the stator temp 3c. That is something because the effect temperature has on magnet wire insulation is anything but linear.

What I really suspect is that a little resistance is going to have to be added to each of the 3 wires between the stator and voltage regulator. Once again complex, but a better educated guess is about 0.2 ohms, which should derate the stator output to around 370 watts by my calculations and assumptions.
Thanks Joel!

I've been out riding for the last few days on the coast ... no e-mail

The 0.2 ohm series resistors would be an "easy" fix maybe ...
I started thinking about wattage .... To produce 400W each stator leg needs to be putting out about ~9.5A

9.5A^2 * 0.2 ohms = 18W or 54W total ...

That's a high-side and simplistic estimate done by by a guy with very rusty EE skills.

It got me thinking that the size of the heat sink on the stock R/R does not seem any too "generous" in size given that it needs to be able to disappate something like ~250W of surplus output from the stator when nothing was drawing power on the bike other than basic requirements & low beam headlight.

I hope one of your R/R mfg. buddies comes up with something nice - thanks for asking them!

As another data point, my F650GS which is now 3.5yrs old and has a new Deka battery installed reads as follows
(using my venerable Fluke 77 meter):

12.90 - resting overnight voltage
13.91 - stable idle
13.65 - 3K RPM

JRWooden is offline   Reply With Quote