Solid State Power Box for XS650

posplayr,

You may want to relocate the 20 A fuse. As shown, if it blows or just comes loose the regulator may become erratic and produce a higher than normal voltage without the smoothing influence of the battery. In general, if the main fuse blows, you want to cut off all sources of power as well. The output from the reg / rect should go directly to the battery and then the combined reg / rect output and battery are fused to the fuse box or to your device.
 
pamcopete,
Interesting point you bring up and I'm sure has many aspects to consider. First I would need to review some schematics, but I know for a fact that all GS Suzuki motorcycles are wired with what is called "the T" . That is a fused primary wire from the battery is connected to the an unfused R/R primary wire (just like the SSPB). The common point is the red primary power source to the ignition switch.

As you point out, if the bike is running and charging enough to sustain the electrical loads (less battery charging currents) and the main fuse blows due to a mechanical failure (i.e. vibration induced) the bike will keep running without the battery being connected. And yes without that battery to load the R/R the chopping voltages from the R/R will be applied to the electrical system.

So we agree on that, but the first question I would put to you is, Would you not want the bike to keep running? In what circumstances are you sure that with the bike running you want it to suddenly quit even if it is in the rare circumstance that the main fuse failed mechanically? The main fuse especially a 20Amp fuse is going to have a very long life indeed especially compared to the much smaller 10 amp fusing members. I think that best answer from a product safety standpoint is to not endanger a rider by shutting down the bike at an inopportune time and as a result getting the rider either injured or killed. Suzuki did it this way, and I think it is best. Different methods of connection have been discussed at the GSR at length and I have posted an analysis there of what the differences are generally to everybody's satisfaction that the "T" method is best.

While I'm not sure exactly what your configuration is that you are describing, but if you want to make sure you don't set your bike on fire, there must be a main fuse between your battery and anything else that could short (you describe r/r direct to the battery presumably without a fuse). Historically for the GS and I assume any other bike with an alternator, you have to guard against a rectifying (blocking) diode shorting out and providing a straight path to ground for the battery. Without a fuse between the battery and the R/R (as the "T" provides) then you will surely burn up a great deal of the harness and likely start a fire. The battery has veny low internal resistance and can provide plenty of current in such an event.

On the GS's at least, I'm pretty sure when these diodes tend to blow it is at startup stresses and the bike will quit immediately. This is evidenced by bikes that keep blowing main fuses when the owner attempts to start them, In these cases the R/R can be removed to confirm it as an issue as the main fuse will quit blowing. In all of my discussion above I have just considered standard UJM electrical/charging system design. In this case the "T" is prefered and the potential electrical damage is just the lesser of two evils. But when one evil is rider hazard, the approach that minimizes that should always be selected.

As far as the SSPB implementation of the same battery fusing (i.e. the "T"), the SSPB is designed according to modern automotive guidelines(e.g. ISO 7637-2:2004, SAE J1113 etc.). As such, it is designed to absorb large transients primarily by shunting them to ground. As currently designed, anything at 20V and below, is allowed to pass on to the electrical system. By about 22V and above that level of shunted through what amounts to a 3 Amp fuse. While fusing is generally related to a time current product, if and when this 3 amp fuse(conducting shunting currents above 20V) blows, the SSPB will disconnect from everything.

It would be an interesting thing for me to test, but I'm not sure I would want to do it on my bike without removing anything that might be sensitive. Basically it would involve running down the freeway and pulling my main fuse (or insert an inline switch). Under typical load dump conditions you should expect +/- 100V current spikes which the SSPB would handle well. It is the low voltage 18-22V stuff that is in the middle that would need to be evaluated.
 
posplayr,

As you have likely noted, the conversion to a PMA type alternator is very popular with XS650 owners. As you know, there is no control over the voltage or current output from a PMA so with the fuse as shown the output from the PMA regulator would be at maximum in the event of a partial short and that could lead to overheated wiring or a fire as well. A dead short would blow the battery fuse, but the PMA would continue to produce maximum power in the time it takes for the engine to stop running. In fact, it could be worse because the PMA is in parallel with the battery so if the PMA was supplying 15 Amps then the short would have to draw 15 + 20 = 35 Amps to blow the fuse and it's possible that the engine would continue to run with the blown fuse and the PMA would continue to produce power unprotected by a fuse.

Also, in the case of the XS650, a shorted diode in the rectifier does not result in battery current going to ground as the alternator stator winding's are not grounded.
 
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pamcopete,

As you know, there is no control over the voltage or current output from a PMA
Both SHUNT and SERIES R/R's provide direct control over the single of three phase alternator windings. I'm not sure where this comment is coming from. Are unregulated PM alternators installed on XS650s?


so with the fuse as shown the output from the PMA regulator would be at maximum in the event of a partial short and that could lead to overheated wiring or a fire as well.

Most all carbureted UJM's will need about 200 Watts for various DOT approved lighting including ignition coil and charging of the battery. From what I have seen that means that for the Suzuki's the PMA are only capable of providing about 18 or so amps MAX. I would expect most all UJM's to be in this ball park.This is a far cry from the current a the battery can provide (easily over 100 amps). So any shorts between the "T" and the return to the fusebox for further distribution which in the GS case at least is 14 awg is unlikely to burn anything. Further if there is a short on the down stream distributed circuits, then those individual fuses (SIGNAL,IGNITION,HEADLAMP) would blow eliminating the short.

A dead short would blow the battery fuse, but the PMA would continue to produce maximum power in the time it takes for the engine to stop running.

If there is a regulator, I doubt it will remain wide open with battery disconnected. It will likely try and apply the stator winding to the load and then when the voltage goes sky high will pull it away. This will cause a voltage spiking problem but unlikely any large average currents. Apparently you are assuming no regulation which is unusual and not sure why the charging system would be so configured?

In fact, it could be worse because the PMA is in parallel with the battery so if the PMA was supplying 15 Amps then the short would have to draw 15 + 20 = 35 Amps to blow the fuse and it's possible that the engine would continue to run with the blown fuse and the PMA would continue to produce power unprotected by a fuse.

Blow what fuse? the 20A battery fuse of the 10 amp down stream (individual circuit fuses) fuses? The PMA can not generate 35 amps at 14V; it doesn't need to be fused as it can only generate no more than 20 amps MAX. And if there is a short that is downstream then that individual fuse will blow and the load will revert to something back under 10 amps (assuming no battery charging current and one of the offending circuits is gone).


Also, in the case of the XS650, a shorted diode in the rectifier does not result in battery current going to ground as the alternator stator winding's are not grounded.

I don't think that are many PMA's around that were built in the last 35 years that have a stator that is grounded. The regulators are still grounded and the shorts do occur; it is not conjecture.

I'm puzzled by many of your comments unless you really are talking about running an unregulated PMA (i.e. NO Rectifier regulator).
 
posplayr,

As you have likely noted, the conversion to a PMA type alternator is very popular with XS650 owners. As you know, there is no control over the voltage or current output from a PMA so with the fuse as shown the output from the PMA regulator would be at maximum in the event of a partial short and that could lead to overheated wiring or a fire as well. A dead short would blow the battery fuse, but the PMA would continue to produce maximum power in the time it takes for the engine to stop running. In fact, it could be worse because the PMA is in parallel with the battery so if the PMA was supplying 15 Amps then the short would have to draw 15 + 20 = 35 Amps to blow the fuse and it's possible that the engine would continue to run with the blown fuse and the PMA would continue to produce power unprotected by a fuse.

Also, in the case of the XS650, a shorted diode in the rectifier does not result in battery current going to ground as the alternator stator winding's are not grounded.

pamcopete,
I looked at both the summary schematic I did at the beginning of this thread as well as about 5 other XS650 schematics (I got from this site) and they all use the "T" configuration I'm advocating. So from the factory the XS650 and the GS Suzuki are wired the same as related to R/R and battery.

Is this a fundamental change you are advocating for any UJM regardless of regulation? The old field controlled alternators on the XS650 will surely start to shut down due to over voltage spikes if the battery is removed won't it? I have to assume that the PMA upgrades you describe also have Regulators. What exactly happened in the regulator is dependent of the specific type I'm sure, but I doubt any will run open loop (i.e. without regulation transmitting maximum power to the load) with the battery disconnected. Even if they did there is only some much power the PMA will generate even if the engine RPM is up high enough to get to maximum output power.
 
posplayr,

I think that the thing you may not understand about PMA alternators is that the regulator is a shunt type regulator, meaning that it just shunts the excess current to ground. There is no control over the output of a PMA. In other words, if there is excessive voltage, the regulator just shunts the output of the PMA to ground to reduce the voltage. If there is a gross load (partial short) that causes the voltage to decline, the regulator has no effect, but the PMA continues to produce its maximum current.

As far as the conventional configuration of the rectifier and fuse, I am not advocating any particular configuration. Just pointing out the design deficiencies. You are advocating a better system , so you have to address these deficiencies.

In the scenario about needing 35 Amps to blow the fuse, the PMA does not have to produce 35 Amps. It is a parallel circuit, so the PMA produces 15 Amps and the battery provide the additional 20 Amps to blow the fuse, but the total Amps feeding the short is 35 Amps.
 
posplayr,

I think that the thing you may not understand about PMA alternators is that the regulator is a shunt type regulator, meaning that it just shunts the excess current to ground. There is no control over the output of a PMA. In other words, if there is excessive voltage, the regulator just shunts the output of the PMA to ground to reduce the voltage. If there is a gross load (partial short) that causes the voltage to decline, the regulator has no effect, but the PMA continues to produce its maximum current.

pamcopete,
I have no idea why in the world you would conclude that I don't understand what a SHUNT R.R is? If you would like for me to demonstrate, I will point out the two errors in your statement.

1.) All Permanent Magnet Alternators do not use SHUNT regulation. As I mentioned in just the last post there are both SHUNT and SERIES R/R's. You can look as a set of charts I produced that demonstrate the operation of a SERIES R/R compared to a SHUNT R/R here.

http://www.keepandshare.com/doc/4066862/ssr-vs-fh012aa-pdf-may-31-2012-10-20-pm-903k?da=y

2.) The notion that SHUNT R/R's dump current "to ground" is an old wives tale that defies ohms law. Current flows in circuits and so current can't be dumped to ground. The stator legs are shorted completing a circuit. Although the potential of the short is nominally at ground there is no current leaving the R/R to get to ground. Ironically you mentioned before that PMA stators on the XS650 are not grounded (I agreed none of them are), so how do you figure the stator current gets to ground? Through the R/R(-) wire that is "grounded"?

As far as the conventional configuration of the rectifier and fuse, I am not advocating any particular configuration. Just pointing out the design deficiencies. You are advocating a better system , so you have to address these deficiencies.

The better system I'm advocating is in fact the OEM configuration for both the XS650 and the GS Suzuki and probably many more. I even explained why it is a best compromise when considering rider safety. The issues you brought up are valid, but hardly design deficiencies. I will admit, that your analysis of the operation leaves me perplexed as it seems to directly contradict fundamental assumptions of what a PMA is. for example in your statements below:

In the scenario about needing 35 Amps to blow the fuse, the PMA does not have to produce 35 Amps. It is a parallel circuit, so the PMA produces 15 Amps and the battery provide the additional 20 Amps to blow the fuse, but the total Amps feeding the short is 35 Amps.

You need to re-think that one. It is not possible! If the R/R output voltage is higher than the internal potential of the battery (typically 12.8V) then current has to flow into the battery not out. If the R/R output is less than the same 12.8V then the diodes are all back biased and no current flow either into or out of the R/R. You either get current from one of the other not both.
 
2.) The notion that SHUNT R/R's dump current "to ground" is an old wives tale that defies ohms law. Current flows in circuits and so current can't be dumped to ground. The stator legs are shorted completing a circuit. Although the potential of the short is nominally at ground there is no current leaving the R/R to get to ground. Ironically you mentioned before that PMA stators on the XS650 are not grounded (I agreed none of them are), so how do you figure the stator current gets to ground? Through the R/R(-) wire that is "grounded"?

Just to clarify for the interested readers:

This Hayabusa schematic uses a delta-type winding, but if you follow the tiny shunted current flow arrows, you can see how the circuit is a closed-loop during output shunting, and ground is tied to part of the path:

HayabusaPMA.jpg

suzuki-gsx1300-hayabusa-charging-circuit.png
 
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Just to clarify for the interested readers:

This Hayabusa schematic uses a delta-type winding, but if you follow the current flow arrows you can see how the circuit is a closed-loop during output shunting, and ground is tied to part of the path:
suzuki-gsx1300-hayabusa-charging-circuit.png

Very true , but the ground current does not exit the R/R so it is not getting " dumped to ground"; ground current only exits the R/R by sending it back to the stator by short circuiting the stator legs using the SCRs. Whether delta of Wye wound stators, the R/R is and operates the same (of course the voltages and currents vary according to the sqrt(3) ratios associated with those two different configurations).

The SERIES R/R does not do that which is why they are so much better and the Stators last so much longer.

You can find a virtually identical schematic in the 80-83 GS1100E manual with a step by step explanation of the current flow.

Available here.

http://members.dslextreme.com/users/bikecliff/


This point about ground dumping is much more than just of point of technical amusement. Every bit of current that goes out R/R(+) has to return through R/R(-) means that current runs from ground to the R/R(-) not the other way around. When regulating, current flow stops so there is nothing going either into or out of the R/R(-). If you now consider the statement that current is "dumped to ground", it is quite clear that that is a gross simplification at the very least and a easily characterised as a gross misinterpretation.
 
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Wow, that is a massive repository.

Would you happen to know about field excited alternators used in other motorcycle models?

The mechanical regulator type 70-79 XS650 alternators do not use freewheel diodes, as I've seen in automotive Delcos and one other motorcycle (can't remember which one). Not sure about the 80-up regulators.

I've seen some anomalies that could be attributed to the lack of a freewheel diode, and wondered if this should be implemented...
 
Wow, that is a massive repository.

Would you happen to know about field excited alternators used in other motorcycle models?

The mechanical regulator type 70-79 XS650 alternators do not use freewheel diodes, as I've seen in automotive Delcos and one other motorcycle (can't remember which one). Not sure about the 80-up regulators.

I've seen some anomalies that could be attributed to the lack of a freewheel diode, and wondered if this should be implemented...

Certainly do not claim to be an expert on field control alternators, but believe I understand at least the principles on the XS650 as I had reviewed those schematics all before coming here. I recall someone asking me about diodes as I recall. My posts here are not that many so it probably wouldn't be hard to run down that conversation. I think it also had to do with a possible explanation for why you needed a 20 amp fuse when GS's only have 15 amp main fuses.

Anyhow what is the question?

PS I just looked in my PM's and there doesn't seem to be anything there about that diode.

I found this comment from before. I made it based on a discussion with someone from here. A freewheel diode is used to shunt current across a load so it doesn't go anywhere else. It is very much like the SHUNT Regulator in that regard. The SHUNT R/R shorts the stator to keep the power from going to the load. As long as the diodes can handle the transient you should be able to use the same type of device. I would need to see a circuit to be sure.

6.) Apparently the XS650 and it's alternator have some type of voltage kick back when shutting off as evidenced by the 20 amp fuses as well as some of the XS650 owners observations. The SSPB will suppress those negative going pulses.
 
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Yes, we may have touched on that with the 15 vs 20 amp fuse discussion.

The question is: Would the addition of a freewheel/shunt diode be prudent and recommended for stock 70-79 mechanical regulator circuitry (in the rotor power lines)?

It's standard practice to add freewheel diodes to semiconductor controlled inductive circuits, to protect the semiconductor driver from inductive kickback.

This may improve regulator life and performance by reducing points arcing and flutter.

Some anomalies that might be attributed to a lack of freewheel (anti-kickback) diodes in the rotor (field) circuit:

- The rare backfire that occurs when ignition is turned off.
- Failures of semiconductor contraptions added to these early models.
My first el-cheapo digital voltmeter eventually failed (no reverse polarity protection)
My second digital voltmeter (with reverse polarity protection) works fine

A couple years ago a member here inadvertently wired her LED neutral light backwards, and reported that the light would glow for a couple seconds after switching 'off' the ignition.

I thought I'd ask before pursuing this....
 
posplayr,


Yes, there are different ways to regulate the output of a PMA and I agree that shunting to ground is an oversimplification, but the current is shunted coming from the winding's of the stator in the simplest type of regulator. However, this shunting action only occurs when the voltage equals the desired regulated value. When the voltage is less than the desired value, such as when the engine is at low RPM's or there is a high load condition, such as a short, the regulator does nothing and the PMA is free to produce its maximum current output, unregulated. That is the situation used to point out the 35 Amp scenario. A partial short will cause the voltage to decrease at the junction of the battery and output of the regulator thus eliminating the function of the regulator so both the battery and the PMA will supply current to the junction of the two sources in parallel. Your answer to this scenaroi assumes a normal operation with a fully charged battery and in that case the battery will not supply any current and the PMA will carry the entire load, but my hypothetical scenario was for a partial short that would cause the voltage to decrease below the float voltage of the battery so the battery would then contribute to the current demand of the short. Of course, it gets a little more dynamic than that, because as the battery supplies current to the short it will discharge to the point where its voltage is too low to cause any current flow to the short through the fuse so the entire scenario of the 35 Amp will be short lived but depending on the severity of the short circuit the flow of current from the battery could exceed 20 Amps before it discharges below the voltage at the junction of the PMA and battery.

In any event, I am not trying to shoot down your new product. I am all for any new product that will help keep the trusty XS650 on the road, but in my experience, I have found that there is a tendency to focus on the "gee whiz" aspects of a new product and lose sight of the front end, in this case, the source of power to your product. You say that many aspects of your product are found in other more modern motorcycles but that doesn't mean that those features are perfect and now is your chance to improve upon them. As a minimum, I would suggest a different scheme for the PMA setup as apposed to the stock conventional field excited type of alternator. The conventional alternator takes care of load anomalies intrinsically because it depends on the system supply of current to excite the field. The PMA, on the other hand, ignores high load conditions, such as a short circuit, and just continues to produce the Amps.

Both types of alternators can produce destructive high voltages for certain types of failures of the regulator. The PMA is more prone to this type of failure. I would like to see some protection for this problem in your design. (Perhaps it is already there and I just failed to see it :doh:)
 
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Yes, we may have touched on that with the 15 vs 20 amp fuse discussion.

The question is: Would the addition of a freewheel/shunt diode be prudent and recommended for stock 70-79 mechanical regulator circuitry (in the rotor power lines)?

It's standard practice to add freewheel diodes to semiconductor controlled inductive circuits, to protect the semiconductor driver from inductive kickback.

This may improve regulator life and performance by reducing points arcing and flutter.

Some anomalies that might be attributed to a lack of freewheel (anti-kickback) diodes in the rotor (field) circuit:

- The rare backfire that occurs when ignition is turned off.
- Failures of semiconductor contraptions added to these early models.
My first el-cheapo digital voltmeter eventually failed (no reverse polarity protection)
My second digital voltmeter (with reverse polarity protection) works fine

A couple years ago a member here inadvertently wired her LED neutral light backwards, and reported that the light would glow for a couple seconds after switching 'off' the ignition.

I thought I'd ask before pursuing this....

So you are asking about a mechanical regulator not a mechanical alternator?
Pamcopete has described in pretty good detail the pitfalls of indirect control of voltage, so prudence would dictate following his recommendation for a solid state regulator that actually regulates directly off of voltage.

http://www.xs650.com/forum/showpost.php?p=113789&postcount=5

Since you apparently don't want to do that, you are left with the variety of ills caused by this mechanical regulator. One of the ill's is that it is producing a negative voltage that is impressed on the electrical system during shut down. This can't be good for anything but apparently is not so bad to cause big problems. So if you are trying to make the mechanical regulator not produce negative voltages at shutdown, use a reverse biased diode across the terminal of the regulator. That will quench any negative voltages where ever they are coming from.

To do this properly you would need at least a voltage scope and ideally a current clamp. If you have neither, you will just have to experiment. If you don't care how big the current is you are quenching then just sick a 10-20 amp rated diode in.

To try and eliminate some of the mystery, I would at least suggest to continue using the reverse biased LED as an indicator of voltage. As soon as you put the diode in the LED should not light.
 

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posplayr,


Yes, there are different ways to regulate the output of a PMA and I agree that shunting to ground is an oversimplification, but the current is shunted coming from the winding's of the stator in the simplest type of regulator. However, this shunting action only occurs when the voltage equals the desired regulated value. When the voltage is less than the desired value, such as when the engine is at low RPM's or there is a high load condition, such as a short, the regulator does nothing and the PMA is free to produce its maximum current output, unregulated. That is the situation used to point out the 35 Amp scenario. A partial short will cause the voltage to decrease at the junction of the battery and output of the regulator thus eliminating the function of the regulator so both the battery and the PMA will supply current to the junction of the two sources in parallel. Your answer to this scenaroi assumes a normal operation with a fully charged battery and in that case the battery will not supply any current and the PMA will carry the entire load, but my hypothetical scenario was for a partial short that would cause the voltage to decrease below the float voltage of the battery so the battery would then contribute to the current demand of the short. Of course, it gets a little more dynamic than that, because as the battery supplies current to the short it will discharge to the point where its voltage is too low to cause any current flow to the short through the fuse so the entire scenario of the 35 Amp will be short lived but depending on the severity of the short circuit the flow of current from the battery could exceed 20 Amps before it discharges below the voltage at the junction of the PMA and battery.

I think your 35 amp scenario is entirely conjecture and you have never measured it or anything to indicate it. It is physically impossible for typical motorcycle the PMA to produce anything in excess of 20 amps and even then that is only at high RPM where an unregulated output would push a battery terminal voltage to 17-20V. It should be clear that no matter what state or charge a 12V battery has it is not going to be discharging with +17V at the terminals. Therefore it is impossible to the R/R and the battery to both contribute current to the bike's electrical system. The only thing that can produce 35 amps is the battery and that is why there has to be a series fuse as close to the source as practical. That is the main reason for the "T".


In any event, I am not trying to shoot down your new product. I am all for any new product that will help keep the trusty XS650 on the road, but in my experience, I have found that there is a tendency to focus on the "gee whiz" aspects of a new product and lose sight of the front end, in this case, the source of power to your product. You say that many aspects of your product are found in other more modern motorcycles but that doesn't mean that those features are perfect and now is your chance to improve upon them. As a minimum, I would suggest a different scheme for the PMA setup as apposed to the stock conventional field excited type of alternator. The conventional alternator takes care of load anomalies intrinsically because it depends on the system supply of current to excite the field. The PMA, on the other hand, ignores high load conditions, such as a short circuit, and just continues to produce the Amps.

While it is obvious that having any technical discussion as to these battery/ R/R connections are going no where, I will only say that unlike the XS650 the GS Suzuki's came from the Factory using SHUNT type R/Rs with the Permanent Magnet Alternators (PMA) and they are all wired with the "T". There is nothing changing the basic design criteria when talking about an field controlled alternator v.s. a PMA. There is no history that I'm aware of on the multitude of GS bikes running around that would indicate in any way that there are 35 amps somehow dumped into the electrical system when wired as a "T". The most kind I can be is that your proposition is total conjecture and without much technical basis.

Both types of alternators can produce destructive high voltages for certain types of failures of the regulator. The PMA is more prone to this type of failure.

You have now changed the subject to destructive voltages vs. the previous discussion of destructive (yet fictitious) currents. Yes there are high voltages possible but the fusing has nothing to do with it. There could be 10,000V and not blow even a 1 amp fuse. Fusing is not voltage protection so I won't entertain this comment any further.


I would like to see some protection for this problem in your design. (Perhaps it is already there and I just failed to see it :doh:)


The SSPB is designed to meet the full set of test condition in ISO 7637-2:2004. If you research the automotive design standards you will have some idea of what voltage protections exist in the SSPB. For those that do not know that means surviving +/-100V load dump pulses. This has nothing to do with the primary fusing.

EDIT: I realize perhaps that you are describing load dump in your description. Dont let me put words in your mouth. If you are I agree it is possible to have very high currents for very short periods of time but this has nothing to do with fusing as fusing will do very little to protect against it. These are two distinctly different sets of design criteria.
 
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Well, I certainly didn't intend to get you upset. I will reduce my hypothetical scenario to 30 Amps. 20 from the battery and 10 from the PMA. In your answer, you continue to use a high voltage to show that the battery could not contribute to the total current in the event of a partial short, and of course I agree. What I have described is a partial short that would reduce the voltage to something less than the nominal battery voltage so that both the battery and the PMA would then supply the excess current caused by the short. Once the voltage goes below 14.5 Volts, the PMA regulator no longer does anything so the PMA is then free to deliver whatever its maximum current capability is to serve the demands of the short. Likewise, the battery would also contribute to the excess current demand from the short once the voltage has dropped below the nominal charge of the battery, typicall 12.6 Volts, so both the PMA and the battery would feed the excessive current demands of the short. The batteries contribution would decline as the charge diminishes, but in the time that the battery is providing current to the short it could blow the 20 Amp fuse, but the PMA would be supplying its maximum output of 10 Amps so the total current being fed to the short would be 30 Amps.

Yes, I did introduce the issue of high voltage from both types of alternators due to a faulty regulator and, yes , I agree that has nothing to do with fusing. I was hoping that you could include some protection from high voltage in your design as that is a more common occurrence. In the case of the stock field excited regulators, you could provide a cutoff to the current to the regulator if it was controlled from your product as I think that you have voltage sensing capability and the regulator is powered from your product. Even if the faulty regulator was uncontrollable, you could cycle it on and off to maintain a suitable average voltage to the battery and provide an alarm to the rider.

The PMA would be a bit more challenging. Using the same algorithm as the stock alternator, you could perhaps introduce a relay that is switched on and off in response to the high voltage sensed at the battery to maintain a good average battery voltage.

An answer to these over voltage issues would be very useful, so I am dismayed that you "won't entertain this comment any further."

Also, I believe that there is a separate set of ISO electrical standards for motorcycles and mopeds so the use of automotive ISO standards may be inappropriate.
 
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I've been considering putting a PMA on my XS, but the first thing to be connected to it will be a SH-775 SERIES reg-rec, as I (and many other GS owners) are now, through experience of them, utterly convinced of the efficacy of them.
In the meantime, the original mechanical r/r was sometime replaced by a PO and the EOM alternator soldiers on with a solid-state r/r of unknown origin, but it's doing its job well enough. With a clean up and brush inspection, it was all fine and I'll continue to run it until it gives trouble, but after that - PMA and Shindengen SH-775, for sure.
 
I've been considering putting a PMA on my XS, but the first thing to be connected to it will be a SH-775 SERIES reg-rec, as I (and many other GS owners) are now, through experience of them, utterly convinced of the efficacy of them.
In the meantime, the original mechanical r/r was sometime replaced by a PO and the EOM alternator soldiers on with a solid-state r/r of unknown origin, but it's doing its job well enough. With a clean up and brush inspection, it was all fine and I'll continue to run it until it gives trouble, but after that - PMA and Shindengen SH-775, for sure.

Waiting until the stock OEM alternator "gives trouble"..........................you may be waiting a long time. I've been using the stock alternator for over 8 years now, and it very reliably puts out 14.2 volts as I drive down the road. Once you remove the original stock rectifier and the stock mechanical regulator (1970 to 1979) , and replace them with new solid state rec/reg units, the charging system works extremely well.
 
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