Stella - 1977D survivor, back on the road.

[weekendrider]

I agree with the no lights testing and it will be only as dangerous as you make it. You know we got along with hand signals for a day or three before turn signals and brake lights. They work so well to get others drivers attention I still incorporate them in conjunction with todays modern lighting.

 

[DanielBlack]

Oh, and the last two rectifiers were both 50A, purchased together. They both failed on the neg side as open shorts. The first rectifier was also Chinese, purchased separately, 30A, and failed a bit differently. The pos side diodes failed open, creating a direct short to ground through the SSR via the yellow wire.

I'm still not sure of how my working lighting circuit could be the issue, but I'm game for a test.

Two Windy Nation rectifiers are on their way, as linked to by 5twins.

 

[DoubleE]

Battery good, rotor good, brushes good, VR new, stator good. 3 blown rectifiers. Let's hope it is a couple sets of bad batches. Still, my stator (75B) puts out a max of 11 amps. This seems well under the 50A rectifier you have. If the stator is good, and everything else specs out, then Pete may have the answer with the connections. I hadn't realized that corrosion can travel up into the wire housing until seeing it here on the forum.

This may be a bit extreme, but you could put a set of 3 fuses (20A?) in your whites before the rectifier. If these blow, it points to a problem with the stator/regulator (it could also save the new rectifier). Again, gurus have forgotten more than I'll ever know. Carry on, you'll get there.
ee

 

[Paul Sutton]

Tell me if I am wrong, but I do not think your regulator voltage control is particularly good, unless it is an old relay type. If it is solid state then it should hold very closely to its preset (14.2V drifting to 13.9V seems too great a deviation to me a non-expert). I always see 14.2V, what do others see with their systems?? Do those with permanently mounted voltmeters see much drift, or systematic drift from say 14.2v down to 13.9V?? I did read somewhere recently that interruption to the field winding due to a poor connection can cause spikes that will damage electronics - Perhaps??

 

[TimeMachine]

I wish I could "step it up" and contribute (DoubleE) badly !.. being limited in ability electrically I am just extremely particular about clean contacts, order, and only one step at a time ! once the handgrenade has been thrown in the mix, no matter how knowledgable you are, the variables multiply. Being very particular and able to reason is my best tool.. that and thinking very much which DB is surely doing. I only hope for enjoyment of motorcycles and do encourage ! It is barely Spring DB you will ride ! -RT

 

[Paul Sutton]

See: https://en.wikipedia.org/wiki/Load_dump

Extract from Above: The windings of an alternator have a large inductance. When the vehicle battery is being charged, the alternator supplies it with a large current, the magnitude of which is controlled by the current in the field winding. If the battery becomes disconnected while it is being charged the alternator load suddenly decreases. However the alternator's regulator cannot quickly cause the field current to decrease sufficiently, so the alternator continues to generate a large current. This large current causes the voltage on the vehicle bus to increase significantly -- well above the normal and regulated level.

All the loads connected to the alternator see this high voltage spike. The strength of the spike depends on many factors including the speed at which the alternator is rotating and the current which was being supplied to the battery before it was disconnected. These spike may peak at as high as 120 V and may take up to 400 ms to decay. This kind of a spike would damage many semiconductor devices, e.g. ECUs, that may be connected to the alternator. Special protection devices, such as TVS diodes, varistors which can withstand and absorb the energy of these spikes may be added to protect such semiconductor devices.

Various automotive standards such as ISO 7637-2 and SAE J1113-11 specify a standard shape of the load dump pulse against which automotive electronic components may be designed.

There can also be a smaller inductive spike due to the inductance of the stator windings. That may have a larger voltage, but it will be for a much shorter duration, as relatively little energy is stored in the inductance of these windings. Load dump can be more damaging because the alternator continues to generate power until the field current can decrease, so much more energy can be released.

 

[TwoManyXS1Bs]

Wow, busy forum recently.

We need those dowsers from the “Water Witch” thread to step up there game and start dowsing for electrical gremlins.

Uh-oh.

Well, here's the take from someone who uses a smoke detector as a cooking timer.

As far as load-dump and such, it's not so much as the output from the stator windings, but the interrupted current flow in the rotor. Modern regulators, and those semiconductor regulators used on 80-83 bikes shouldn't have this problem.

http://www.xs650.com/threads/alternator-rotor-inductive-kickback.42605/

...Max charge slowly dropped from 14.2v at the start down to 13.9v ...

... drift, or systematic drift from say 14.2v down to 13.9V??

My 2 thoughts on this.

1- If the voltage sense of the regulator and the voltage tap point for the voltmeter are at different locations, this voltage variance could just be caused by resistive current between those two points.

2- If one diode breaks down, generator output is reduced, regulator increases demand, and the remaining 2 diodes would need to carry more current, increasing heat on them, leading to cascade failure.

...if there is a break in the windings when heated, then as the windings cool (from no current) they establish continuity again and the amps spike because the bike is turning 3-5K rpms?

There *might* be a break, frame short, or crossover, in the windings, creating intermittant voltage/current surges in their outputs. I think there's a total of 24 field posts in the stator, and for a 3-phase that would be 8 posts per phase. I have no idea if those posts are wound in series, parallel, or a combination. But, an intermittant break, or short to frame ground, or crossover to another winding, could cause strange output spikes.


But, by the book, the stated rating of the better import rectifiers is well above what the XS650 stator can throw at them. But, some of those rectifiers are available in as low as 50 volt ratings, and lower currents, which would be risky. Wonder if any of those got relabeled and slipped into the supply stream.

... I have spent my entire career using electrical and electronic equipment and the number of actual electrical component failures (aside from burnt out bulbs of course) that I have experienced could be measured on the fingers of one hand (well, maybe two - but it's been nearly 40 years). It simply doesn't happen that often...

Pete, in your professional environment, with industrial and automotive grade electronics, I would agree. But in the electronics hobbyist arena, flooded with consumer grade components, low quality stuff is somewhat expected. Many of us buy items in bulk, then hand select what works, or within margins, toss the junk.

...Two Windy Nation rectifiers are on their way, as linked to by 5twins.

Given the situation, a prudent move.

If you like, you could send me the failed rectifiers, and I could crack into them and try to do post-mortems. Which includes dowsing rod whippings. PM if you want to pursue this...

 

[TwoManyXS1Bs]

Another item to consider is the battery's demand on the system, during charging, and especially during fully charged. I still monitor my batteries old-school, by controlling and observing charging currents and voltages.

My old variable power supply, also used for battery charging.


As the battery reaches full charge, the current draw should drop to no more than 2 amps, 0.5 amps being ideal. I've serviced many batteries that demonstrate normal full charge voltages and load tests, but will still draw up to 20 amps at their full charge state. These will overtax a charging system, and will tend to boil-off. Best replaced, but difficult to explain to a customer...

 

[DanielBlack]

Wow, plenty of stuff to chew on here. My work is currently getting in the way of moto pursuits, so I'll have to dig in to this tonight. Thank you, gents.

 

[TimeMachine]

Voltage regulator "data" today. Because of RAIN I've just tested my other XS's VR for output. Recently posted stock results confirmed a little low voltage till 3k(gapped at .016) , Today I've pulled my other stock VR(gapped at .014) to compare. 13.0 @ 1500rpm, 14.5 @ 2k, 15.3 @ 3k ! Done ! Game over.. maybe thats why my other 78 was blowing fuses ? Conclusion, these stock charging systems are plenty powerful ! No desire to play/test the chinese after market.. now I am off across town to pick up a 3rd used Stock VR ! -RT

 

[retiredgentleman]

If you had the world's most perfect regulator, your battery voltage would only rise to 14.1 volts. Any voltage above 14.1 volts just causes a loss of water from the battery, and achieves nothing. However, because its not a perfect world, a range of 14 to 14.5 volts is considered acceptable. My voltmeter on my bike always sits at 14.2 volts when driving down the road, but because of where I am measuring, I know my battery is seeing 14.3 to 14.4 volts.

 

[TimeMachine]

this is my Yamaha book, seems too high but my VR's are both high and low by spec. But not at 2k.. Im really trying to find the sweet one.. any input ? Thx, -RT

 

[retiredgentleman]

Yes, I've seen the 14.5 plus or minus 0.5 volts before. That's from an old manual. They must have believed that to be correct back in the 1970's and 1980's. However, time and technology moves on, and I think you will be unable to find any credible modern reference source or text book that agrees with those numbers. Like I said, 14.1 volts is the preferred voltage, with an upper limit of 14.5 volts, for a lead/acid battery.

 

[TimeMachine]

Okay , Thank you rtgman , You are a truly valued influence ! -RT

 

[MaxPete]

Well, lots to chew on here.

ALL: as noted, I'm not an expert in electrical stuffology and Daniel - please correct me if I'm wrong here - but you might all want to note that Daniel has converted his bike to LEDs - I think every bulb except the headlight. His mods also include a very cool brake light pulser and dual brightness rear signals - without the butchery involved in making dual filament bulbs fit. The work has been beautifully executed with top quality components and really first rate workmanship. I want to make precisely the same mods on Lucille and the cafe bike too.

My point is however, that he has reduced the electrical load on Stella by a fair bit - would that make a difference in charging system performance?

Anyhow, I'm sticking with my earlier hypothesis that there is something else wrong - and that the rectifier failures are a symptom. I really like 2Ms offer to do autopsies on the failed ones.....

Pete

 

[TwoManyXS1Bs]

Most of my XS1B riding is daytime, no lights, charging system handling just the points ignition, gear indicator, volt/temp/time meter, and AGM deer-feeder batteries. My batteries only draw 0.2 charging amps. So, this would be low-demand as well. But, it's still using stock components.

Having (3) rectifier failures in a row certainly sounds like "beyond random occurrence", and suspecting something else is definitely warranted.

If those rectifiers were indeed performing at their ratings, the currents (30-50 amps) and voltages (>1000 volts), if constant, would do a number on the stator wires and windings.

So, what's left would be some pretty serious spikes. Would need to hang a scope on those lines to see those...

 

[Paul Sutton]

A few weeks back I posted an Ebay link with a warning about rectifiers for old single phase bikes. The upshot is that 100Volt max rating is too low but 400V is fine. It is hard to imagine spikes exceeding 1000V as pointed out above. Also, the bike in question is running Boyer electronic ignition and this probably would fail due to very high spikes.

We know that the rectifier runs for a while before failure and initially it is not excessively hot to the touch. My thinking at present goes with all three diodes burning out in sequence as the load transfers to the remaining active diodes as pointed out in Entry 487 by TM. Perhaps the voltage drift observed (14.2 - 13.9) is the result of a single phase failing at the rectifier??? Is this situation mirroring the PMA overheating when too much current is being dumped to ground i.e. there could be a short to ground??? A short to ground post rectifier should give smoke or blow a fuse because it will drain the battery. A short to ground of 1 phase winding would not show up in the fuses but may show up as rectifier overheating due to increased load on the other 2 phases.

Could be difficult to track down an intermittent short. Someone suggested (my apologies for forgetting who) inserting fuses and this interests me. Where should they be located?? A fuse on all 3 phase wires, as suggested, might not tell you directly which stator winding is shorting but will indicate if excessive currents are being transferred to the remaining two phases - if the fuses are close to the stator they will also show if the short is post-stator. I would also add a fuse to the field winding. Perhaps 10A for stators and 5A for the rotor - I say 10A because I understand the 16A max rating is shared between all three phases to varying degrees (perhaps 7.5A may be better - let the more experienced make this call).

Off for a spin, blue sky and zero wind.

Note: Using fuses is quite low-tech, but a cool/clever idea!

 

[DanielBlack]

Yeah, a whole lot of input in the last 24hrs, thank you very much gentlemen.

To me, the theory of cascading failure through the various rectifier diodes is very likely. It matches behavior I have observed informally. At this point, I'm leaning towards the issue being isolated to the rectifiers. I don't see them working near, at, or past their stated 30/50A ratings and they are failing anyway.

Yes, the rewire project could have caused issues such as wiring mistakes, bad connections, and such, but I was pretty careful and running complex systems of power and control is what I do for a living.

As to charging components and their likelihood of being the culprit, just before this electrical overhaul the charging system was perfectly fine. Maybe a bit low, 13.8v, but regular for a thousand miles. Stator, rotor, regulator, and battery all served perfectly well for those 1000 miles and the only thing that's new is the rectifier and wire. The wire and connections are new, checked, double-checked.

In addition, as Paul noticed, when a new rectifier is installed I get a well-regulated 14.2v for at least a short while. As that number begins to degrade the only place I can find any change is at the rectifier. After that 30m driveway test and 27mi spin, max battery voltage had dropped from 14.2v to ~13.6v. Measuring the rectifier diodes at that time showed a slightly greater voltage drop on one phase than I had seen when new. After a overnight cool down and 5 more miles, all three neg diodes were toast. Seems to me like evidence of the cascading failure.

Putting the old original rectifier in gives me the same 13.8v I had before the rewire. The other components seem to be fine. I bet when I install one of the new Windy Nations I'll see the full 14.2v we expect.

So, here's my plan.

Install permanently mounted voltmeter. This has been my plan all along, I had only succumbed to the Perfect getting in the way of the Good, and dammit, I wanted to find a small analog meter of better quality than the ones behind the counter at O'Reilly's. Oh, well.

Install new Windy Nation rectifier. Ride test it first without lights for ~30m. If voltage is still at 14.2, reinstall the lights fuse and go for another 30m ride.

With the onboard voltmeter, as soon as the max charge begins to drop I will pull over and grab a snapshot of rectifier diode readings. I had seen a change here when the last rectifier began to degrade.

I could use the original rectifier, but at it's best, it only puts out 13.8v when regulated for 14.2v. It would be a confirmed weak spot in a system that shows it has potential for 14.2v, no?

If I still have problems with the first Windy Nation I think we'll be able to confidently assume a problem somewhere else and dig deeper. But until then, my money's on defective rectifiers.

And yes, I am taking 2M up on his gracious offer to post-mortem the dead rectifiers.

 

[MaxPete]

Good plan Daniel and I completely support Daniels assertion that he does a good job on wiring system design and execution.

His LED lighting set-up on Stella is a genuine trendsetter IMO - and I will be implementing it on Lucille and the '81 Special-to-Cafe bike as soon as this is all sorted out.

Cheers and best of luck DB.

Pete

 

[DanielBlack]

Thank you, Pete. I greatly appreciate the cheerleading.