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Jules
| | Posted on Monday, August 02, 2010 - 05:13 am: | 
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Having only had the harness upgrade last week I have been keeping a close eye on my voltages whilst riding. It seems to stay at 14.0 or 14.1 irrespective of revs above 2K. At idle, with the fans on it never drops below 13.5, even if sat there for quite some time.
I tend to ride it like I stole it anyway - but I guess I can't use the stator as an "excuse" for that LOL |
Timtowtdi
| | Posted on Monday, August 02, 2010 - 07:36 am: |
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Ok, so the stator is its own heat source. So by keeping the rpm up, we are hoping to be running the charging system at a lower duty cycle instead of full fielding it. Right? It really has nothing to do with CT then?
One more question for everyone experiencing charging system problems. Have you tested your battery? If so, how?
Tim |
Jdugger
| | Posted on Monday, August 02, 2010 - 07:54 am: |
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> It really has nothing to do with CT then?
That would be my take on it. The windings get hot themselves and melt through the insulation. No amount of coolant in the world is going to really help with that problem.
Keeping the revs up actually reduces the heat from the electrical demand on the stator since it has "more chances" to produce the required current. (I'm not an EE, so forgive my horrible description.)
My comments about keeping the revs up on these bikes is partly this, but also just because the bike *runs* better around 5k+. You are in the heart of the power band, and vibes are smooth, and the throttle response crisper. Before the new OEM fuel maps, running the bike near the middle of the motor's range also cured the stumbling.
I think a lot of people get frustrated thinking I'm telling them "how to ride". I could give a crap less what someone does with it; I'm just saying what the practical reality is with these bikes. Let's face it, there are bugs, and HD ain't gonna fix them. So, we can belly ache about it, or we can learn to do some simple things to "ride around" the issues. In my opinion, these "ride arounds" turn out to make the bike more enjoyable from a sporting perspective, anyway.
(Message edited by jdugger on August 02, 2010) |
Timtowtdi
| | Posted on Monday, August 02, 2010 - 08:55 am: |
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Thanks for the explanation. I think I understand now.  |
Tpoppa
| | Posted on Monday, August 02, 2010 - 08:59 am: |
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So by keeping the rpm up, we are hoping to be running the charging system at a lower duty cycle instead of full fielding it.
Stators always run at 100% output, for a given RPM, except in the case of the charging harness upgrade. It shuts off one phase below a certain RPM, so it runs at approx 66% output until the 3rd phase kicks in.
A stator should be producing more power than is needed, the excess power/heat is shunted to ground by the voltage regulator.
Since the harness upgrade, my bike does not produce enough power at idle, and starts drawing from the battery. If I get stuck in heavy traffic, I'll get a battery light at almost every red light (voltage dips below 12.0). Occasionally, I'll get a SYS VOLTAGE ERROR. Twice, I've watched it idle down to the 10s where it stalled. The dealer has replaced the stator, regulator, and battery.
(Message edited by tpoppa on August 02, 2010) |
Jdugger
| | Posted on Monday, August 02, 2010 - 10:21 am: |
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> Stators always run at 100% output, for a given RPM
Sort of.
Remember is the draw/demand on the stator that generates the heat as the windings pass through the magnetic field. Load/Current is drawn from the stator more so than the stator outputs it.
The regulator makes the draw 100% of the time by shunting current to ground, but not all regulators work this way. It's a pet theory of mine you could put an '08 regulator on the '09 stator and you might have charging problems, but you wouldn't have stator ones...
(Message edited by jdugger on August 02, 2010) |
Tpoppa
| | Posted on Monday, August 02, 2010 - 11:12 am: |
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Remember is the draw/demand on the stator that generates the heat as the windings pass through the magnetic field. Load/Current is drawn from the stator more so than the stator outputs it.
You sure about that? That is true for cars or for the alternator on a Goldwing--more demand = more output. For stators the output is based on the speed the rotor is spinning around the stator. More demand doesn't lead to more output (but it would mean that the regulator has less power/heat to dispose of). It's a 'dumb' system.
Here is a better explanation:
http://faq.ninja250.org/wiki/How_does_the_charging _system_work%3F
The 08s & 09s use the same part number for the regulator. Which is odd since the 09 stator has 20% more output |
Jdugger
| | Posted on Monday, August 02, 2010 - 11:42 am: |
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> You sure about that?
Well, no  I'm no EE, that's for sure. |
Reepicheep
| | Posted on Monday, August 02, 2010 - 12:28 pm: |
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I am an EE (well, an EET, which is probably better equipped to answer the question than an EE  )... and he is right.
If you have a fixed field (in our case big magnets) stator, and a shunt regulator, the stator is always putting out full power and full heat.
On a gold wing, and on cars, you have a variable field alternator. So no fixed magnets, you have one set of windings making the magnetic field, and another set of windings moving through the field generating power. Nice in that you can change the strength of the field to regulate your power.
But the variable field approach has two problems:
1) You have to have a battery to "bootstrap" the whole process to get some current in the field windings to generate a magnetic field. Without it, you are just spinning a coil by a coil with no magnetic field, and you never make any power. So without a battery, it'll never start working. Once you get the field going and the thing spinning, you can draw off some current to run the field and you are fine, but you have to get things started.
2) One of the coils, by definition, has to be spinining. That means they can't just have a wire hooked to them (as it would get all twisted ). So they have conductive "brushes" riding on copper pads on the shaft, and are transmitting the current that way. These brushes are just rubbing, and wear over time, and will eventually need to be replaced. They are "sparky" for this reason as well, the brushes are constantly jumping little gaps.
So actually, the Buell design is simplest. The magnets (which need no wires) are on the spinny bit, and the coils (with wires) are stationary.
The shunt regulator is also stone age, and works, but we can (and probably should) do better now. A shunt regulator lets the voltage climb until it hits a threshold, then when it passes it, just shorts the line to ground (with a diode so it isn't discharging the battery through that shunt).
So think of the shunt regulator as a big switch. While the output of the stator (which goes from say 0 to 40 volts once every revolution of the motor) is below 14.0 volts, the output is fed into the battery (charging it up). At the moment all that power being dumped into the battery crosses above 14 volts, the switch disconnects from the battery, and just reconnects and slams the output straight to ground.
This was done in the old days, when there were not a lot of devices to choose from that could switch that kind of current quickly. An SCR (silicone Controlled Rectifier) was cheap and able to be built to handle a lot of current, and worked great.
These days, we have MOSFETS, which work in completely different ways but could solve the problem much better by using a switching regulator design (a whole 'nother topic that books have been written on). But the bottom line is that a good switching regulator will only draw the power it needs, it won't waste any.
That sounds like the miracle solution to the 1125 problem, but it might not be. At low RPM, the shunt regulator isn't wasting that much power, the stator is barley keeping up anyway. And it sounds like that is where the problem is.
At high RPM, when the stator is making power to burn (sorry, couldn't resist ), that's when the switching regulator would spare the stator some mechanical load and lower the current draw.
If it were my bike (and when my bike dies, it will be) I will probably switch to a switching regulator. It would definitely help the 1125 stator issues if they are heat related, but it might not solve them.
Hmmm. Now you have me thinking. Does the updated wiring harness shut down a specific leg of the stator at low RPM? Maybe they know one is not getting oil at low RPM, and they shut that one down. So it's not a matter of getting less heat to the stator as a whole, it's keeping the leg that isn't getting cooling oil from getting hot.
(that's just speculation, the pattern of the winding on the stator may be such that every leg is everywhere anyway... I don't know). |
Dannybuell
| | Posted on Monday, August 02, 2010 - 01:09 pm: |
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Reepicheep - THX I enjoy getting the basics from subject matter experts. |
Tpoppa
| | Posted on Monday, August 02, 2010 - 01:15 pm: |
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Reep,
Very good explanation.
Hmmm. Now you have me thinking. Does the updated wiring harness shut down a specific leg of the stator at low RPM? Maybe they know one is not getting oil at low RPM, and they shut that one down. So it's not a matter of getting less heat to the stator as a whole, it's keeping the leg that isn't getting cooling oil from getting hot.
(that's just speculation, the pattern of the winding on the stator may be such that every leg is everywhere anyway... I don't know).
Yes. The harness shuts off a specific leg. From the pics I've seen, it appears that each leg uses 4 of the 12 poles of the stator (never having unwound one myself, let's call that educated speculation ).
The hotspot/failure point seems to be consistent (again, speculating based on the pics I've seen), its the point where the 3 phases intersect, which would make sense as the hottest spot. This is also the spot where the oil flow seems to be blocked by the adhesive inside the stator cover. |
Jdugger
| | Posted on Monday, August 02, 2010 - 05:04 pm: |
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Reep,
I think the stator is only at 100% because of the regulator, right?
If you put a 2M, 1 Watt resistor across the stator output, it will have less draw and less heat on it than what is roughly a dead short in the form of a shunting regulator; Ohm's law and all, right? (or not?)
Or am I forgetting Jr High science class here? |
Reepicheep
| | Posted on Monday, August 02, 2010 - 06:18 pm: |
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Yes, the stator is only at 100% because the regulator is shorting any excess power to ground.
A resistor in series with a stator leg would cause less current to flow, and reduce the heat in the stator, even with the shunt regulator. It would have to be a substantial resistor though, a soldering iron is only 15 watts (just over 1 amp at 14 volts), and that would be a tricky thing to package on a motorcycle without melting something...
Changing to a switching regulator means the stator only delivers as much power as the bike currently needs. That also means less mechanical load, so you can claim something like a .8 horsepower gain at redline, at least if your battery is charged.
A plus no matter how you look at it, but unncessary on the older bikes. |
Jdugger
| | Posted on Monday, August 02, 2010 - 07:01 pm: |
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Put the resistor in series of the shunt to ground and heat sink the piss out of it against the subframe? |
Freight_dog
| | Posted on Monday, August 02, 2010 - 07:37 pm: |
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Jdugger: riders who keep the revs up -- using roughly the middle of the motor's range -- don't have the problem.
Not true. Mine died at 800 miles, ON the freeway AT 6000 rpm after running for nearly an hour at those speeds/revs. I tried dropping a gear and revving higher, it only made things worse. I was able to nurse it home by going to 6th and running about 4k. Furthermore, this was March, the ambient air temp was in the upper 50's
(Message edited by Freight_dog on August 02, 2010) |
Jdugger
| | Posted on Monday, August 02, 2010 - 07:51 pm: |
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> Not true.
Did you ride the bike CONSISTENTLY with the revs above 5k, or just that time? |
Ezblast
| | Posted on Tuesday, August 03, 2010 - 01:15 am: |
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Very consistently. |
Tpoppa
| | Posted on Tuesday, August 03, 2010 - 12:04 pm: |
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At low RPM, the shunt regulator isn't wasting that much power, the stator is barley keeping up anyway. And it sounds like that is where the problem is.
I would agree. There is not much excess at low RPM. Then the harness upgrade is taking about 33% of the available power away at low RPM, causing the battery to discharge (at least on mine). I suspect this will extend the lives of some stators, but at a cost of battery lights, SYS Voltage Errors, stalls, etc. |
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