Voltage Regulation

[ajensen]

I have a question about how the GS500 regulates battery charging. My understanding: There is permanent magnet three phase alternator. The A/C current goes to a combination rectifier/regulator. The excess D/C current is dissipated by turning it into heat, presumably through a zener diode.  Is my understanding correct so far? If excess voltage, say beyond 14.7 volts, is turned into heat, what happens if the lighting system uses less current than the original design? For example, LED lightbulbs are more efficient. Is there a danger of over-stressing the regulator/rectifier if there is not enough load on the system?

Much of my experience is from the dark ages of British Lucas electrical systems. A big advance was using a zener diode with a heat sink. Before that, there was no voltage regulation beyond the battery and lights. Therefore, I may be writing some really stupid things when I write about "modern" motorcycle electrics.

[peteGS]

With the stock regulator/rectifier, excess current is actually "shunted" back through the stator, therefore somewhat contributing to engine heat and over time will actually lead to the demise of your stator.

Best charging upgrade you can do is swap out the standard rec/reg for a series unit like the SH775.

The most economical way to get one is to search for Polaris part #4012941, but keep in mind this upgrade is not an unplug/plug conversion and you will need to get the appropriate plugs as well as they use Furukawa type connectors as used on MOSFET rec/regs common on other bikes.

http://easternbeaver.com/Main/Elec__Products/Connectors/R-R_Connectors/r-r_connectors.html

Plenty of info on places to get etc. over on the GS Resources:

http://www.thegsresources.com/_forum/showthread.php?226979-Polaris-R-R-prices-(SH775-Polaris-part-number-4012941)

*I take no credit for this info, definitely all sourced from the GSR.

[TGTwin]

If you use a lower-current lighting system (LEDs), then there will be less energy shunted/wasted, not more.
The power that the regulator shunts is the voltage difference (max voltage - 14.7) times the current. Less current = less power shunted = less heat = happier components.
Considering how few reports you see of rooted coils on stock engines, I wouldn't bother changing the regulator especially if you have a more efficient lighting/electrical system installed.

[peteGS]

It doesn't quite work like that... the GS stator is actually a generator... so that means it generates an amount of power no matter the current draw, which means the charging system needs to do something with that power.

So, either things like the headlight draw current, or the reg/rec needs to shunt it somewhere, which is back to the stator and therefore the excess power is lost in the form of heat.

More modern bikes have alternators, and I believe that is a different story... sorry I can't explain in more reasonable technical terms but I'm just not that smart. I do know the above is fact though as it has been proven by much smarter people than I.

[The Buddha]

PeteGS is generally correct - except in the "more modern" aspect.
The ancient XS650 had that aspect he's talking about, in fact newer bikes like the GSXR's have much smaller but more powerful neo's.
Older bikes had those brushes and what not to create the magnetism there by truly regulating the output of the "alternator".
Cool.
Buddha.

[mr72]

Hey Pete, what do you think about an OEM type replacement part such as this?

http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=272535697781&t=1497555666000&tid=10&category=43976&seller=theropshop&excSoj=1&excTrk=1&lsite=100&ittenable=false&domain=ebay.com&descgauge=1&cspheader=1&oneClk=1&secureDesc=0

My charging system is putting out less than 14v so I am interested in an upgrade but not at a $200 cost.

[ajensen]

I am still confused. I think that the difference between a generator and an alternator is that a generator puts out DC, so there is no rectifier needed. There are permanent magnet alternators and electromagnet alternators. The permanent magnet ones, like on the GS, put out more and more current (up to a certain amount) according to rpm's. The electromagnet alternators can be regulated by making the magnet stronger or weaker--the job of a regulator. Since the excess current of the GS is turned into heat, I am curious about two related   things:

1. How the current is re-routed back to the stater
2. If less current is used by LED bulbs, why isn't there more excess current that has to be turned into heat?

Thanks in advance for any clarification that can come into my foggy old mind.

[Kookas]

1. How the current is re-routed back to the stater

My understanding is that the excess current is turned into heat via resistance in the reg/rec itself, hence the cooling fins on it and why reg/recs fail a lot.

A little reading up suggests that it may also be dissipated into ground, rather than back to the stator.

[peteGS]

Thanks for the clarification Buddha, like I said I'm not smart enough

mr72... I can't really comment on that particular brand/version, all I know is the genuine Polaris version of the SH775 is currently the bees knees over on the GSR (and I have one which works well). They can be had cheaply second hand on eBay also. So far going by feedback I've seen buying second hand ones is ok reliability wise. I have seen people post that there are after market/generic branded versions that are actually shunt not series, which means they're not really a replacement at all. However, if you have under charging, you'll need to verify your stator is good before replacing the reg/rec. If that's not generating enough power, your reg/rec can't make up for it.

ajenson... You're exceeding the limits of my knowledge there However your question 2, yes if you use LED bulbs there is in fact more current that needs to be sent somewhere. If you look at an old GS charging system, one of the three legs of the stator/generator is actually sent via the headlight switch. The reason for this was that with the headlight off, you didn't need the full output of the stator's three circuits, therefore it was easier on the reg/rec to have only two of the three to provide the necessary current to run the basic electrics they had and keep the battery charged. Turn the headlight on and the full output of the stator is added to the charging system and it could cope with the added load of the headlight without draining the battery.

Kookas... Sorry, again, beyond my limits there The thing is, I'm ok with low voltage DC stuff, I've made my harness for my Kat project and done plenty with the 450 harness and so forth, but when it comes to AC and analogue signals etc. my eyes start to glaze over and my mind wanders to where I'd rather be riding...

Just to clarify, I'm not an expert in this field nor trying to be one, I just want to make sure people don't damage stators or reg/rec's or other expensive electrical components or have an expectation of their charging system that isn't right. If there's one major common thing with the old GS/GSX bikes it's that their charging systems out of the factory aren't the best, but there are simple ways of rectifying that and working around the issues that don't have to cost an arm and a leg.

[Big Rich]

Just want to add: the R/R linked above by Mr72 and / or the one Pete is talking about is fairly large compared to the stock unit. So you'll need to figure out a new place to mount it. Luckily it is so efficient compared to stock that it doesn't get nearly as warm, and can be mounted just about anywhere.

And when ordering from Eastern Beaver (awesome business btw), understand he is shipping from Japan..... which is slightly faster than getting something from China.

[ajensen]

Thanks for all the information. Now, I am thinking about going LED and using the recommended rectifier/regulator.

[peteGS]

Good point Rich! I always forget to mention that... I probably don't think of it because I don't run stock electrics...

[TGTwin]

So the original question has really been answered, and I'm no mechanic, but I've been mulling this over from an electrical engineering standpoint and I can't really wrap my head around the "It's always produces X current and voltage regardless of load" logic.
Looking at the wiring diagram, it is listed as a "generator", but in reality it would be a 3-phase permanent magnet alternator (3 coil stator, surrounded by a rotating magnet assembly). These three phases then get rectified and regulated by the rectifier/regulator.
The Rectifier part will just be a diode bridge converting 3 phase AC to DC, and the regulator will just be shunting anything above 14.5v to ground and therefore converting the wasted power as heat (a lot of heat potentially). But this wasted power will still be a function of the current draw of the system. As far as I understand it there is no reason why the regulator would do anything at all if you disconnected the DC wires from it.
I just see no way the generator/alternator would "produce" current by itself, and therefore if using a lower current electrical system (LED), the regulator wouldn't be dumping as much current to keep the voltage at 14.5 v and so wouldn't get so hot.
Is there something really obvious I'm missing? BTW I'm from a mechanical engineering background so that's where I'm approaching this. I used be fairly certain how this worked but now I'm second-guessing myself.

[mr72]

TGTwin you are correct.

Current is always a result of load. It's Ohm's Law, not Ohm's Suggestion.

However for voltage above the zener voltage, the load is the stator, which varies according to rpm, up to the point of magnetic saturation. So in other words it has sme minimum effective AC load, at magnetic saturation, and the effective resistance (impedance actually) increases a little bit inversely to rpm. So it's not really true that the "stator is putting out maximum current all the time". It is true that when the input voltage is above the zener voltage, the voltage difference is applied across the stator as a load. So at lower rpms (say, 2K) the stator voltage may be only slightly above the zener voltage (say zener is 14.4V, and at 2K the stator is putting out 15V). The amount of current is defined by Ohm's Law, in proportion to voltage, across a (somewhat fixed) stator coil impedance. In this case voltage is only 0.6V so current is lower than the case of higher rpms (say, 4K) where maybe the voltage is 50V and therefore the voltage across the stator is 50-14.4 or 35.6V, impedance remains the same (the stator coil didn't change, much), so current increases proportionally to voltage, so in my example the stator would have about 60x as much shunt current flowing through it at 4K rpm than it does at 2K, that is in addition to the load current (lights, charging, etc.).

Now, above some rpm (guessing, 4-5K?) the stator is in magnetic saturation and therefore the current will be limited. I won't really go into that

With the series-type R/R as peteGS suggests, the shunt current basically goes away so you draw essentially load current at all times, which would again put Mr. Ohm back on the throne and make this DC circuit behave like we were all taught it should.

In short, the Zener diodes in the R/R complicate the circuit from an analysis point of view.


EDIT: BTW I am going to take a flyer and try this:
https://www.ebay.com/itm/Voltage-Regulator-Rectifier-Replacement-for-760cc-Polaris-800-Ranger-SH-775/162705185920?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D48739%26meid%3D0b0f06e016ac4972bd648be08719b6dd%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D263270132470&_trksid=p2047675.c100005.m1851

This is a good thread that explains this in some detail:
http://www.triumphrat.net/speed-triple-forum/104504-charging-system-diagnostics-rectifier-regulator-upgrade-2.html

The R/R mfg part number for the series-type is SH-775 and the Canadian seller on ebay above is delivering SH-775 R/Rs from China for like $22 and change shipped.

[peteGS]

See all the above just lost me completely 

The only thing I do know is that tests were done by smart people so I can't really comment... the conclusive evidence though was that with a shunt style reg/rec the engine ran slightly hotter than with the series reg/rec, and I believe the temperature increase was located around the stator area.

I do understand the confusion because my limited understanding of this stuff agrees that the shunting should only ever be through the reg/rec (ohms law is probably the only bit I remember from my college days), so I don't pretend to understand why the stator is affected by it.

Does it mean you should never use a shunt style reg/rec? Probably not, plenty of old GS' around with stock or stock replacement ones without issues, but if the option avails itself I would definitely recommend switching, and they are known to limit the life of your stator.

For a concourse restoration there is no choice, a stock shunt style is the only option there, but for me on a daily rider GS I need to be reliable in all weather conditions I definitely reckon the series is the right way.

Edit: I realise I probably look like a bit of an idiot here and I'm fine with that, like I said earlier I just don't want people to be under a false impression of how the charging system does/doesn't work so they can make fully informed decisions on the right way to resolve issues and make their bikes reliable 

[mr72]

Pete, your input on this subject has been excellent. It sent me searching for alternatives which is a good thing.

The way a zener diode works is basically when you apply a voltage larger than the zener breakdown voltage, then the zener breakdown voltage exists across the zener. So you put the zener in parallel with the load, like in our case the entire motorcycle circuit. So 14.4V exists across the load (across the zener), and the rest of the voltage has to be absorbed by whatever resistance exists between the zener and ground. Ordinarily you'd put a load resistor to limit current, like if you are using a zener as a voltage reference (quite common). But in the case of the GS R/R it appears the only load is the stator coil(s) itself. This is a rather low impedance up to the saturation limit or when you get frequency limiting due to rpm. I mean, the excess voltage is basically AC, so ordinary Ohm's Law for AC circuits applies.

IDK what you'd ever want to limit the charge current to, maybe 10A? In that case you could probably put a 4.7 ohm power resistor in series with the stator common lead (or ground from the stator) but assuming your excess voltage was going to be something like 60V and you'd wind up with about 12A in shunt which means you need a whopping 720W power resistor. Not really likely. Or you could get real tricky and use another zener across the stator in parallel with a smaller resistor to limit the voltage. Say, use a 25V zener and a 100W 4.7 ohm power resistor that would limit the voltage at the stator to more like 35V instead of 60 and cut the current by 40%.

Anyway it's likely that the GS's stator is designed well enough to handle the current while in shunt. And remember it's not DC, it's AC that's being shunt... well, clipped AC. So the duty cycle is less than 50%. I don't think the wiring from the stator to the R/R is nearly big enough for a continuous 25A current draw, that would have to be at least #10 or #8, and this probably explains the melted plugs that are common. But that problem is common to most motorcycles. I'll also point out that nearly all motorcycles use the same zener shunt type R/R and if it was really that big of a problem you'd hear about dying stators all the time. In over a year of diligent reading of this forum and reading a ton of archives and FAQs etc. I have yet to hear of a stator that failed for this reason.

Seems to be the Harley and Triumph guys complaining most about overworked stators. Maybe the Suzuki is just more robust.

Still, if I find my bike is not charging at >14v then I may try the series type from China I posted above. $22, hard to beat.

Again, thanks peteGS for pointing this all out I apologize for the brainstorming and deep digging. I think out loud.

[J_Walker]

the one thing later model GSs got better with, actually under-reported. is SOME wiring on the harness is beefier then the earlier models. plugs are the same however.

[peteGS]

Thanks mr72! I *should* know how a zener works... I did that bit in college but college was... well... 25+ years ago and I haven't really used that theory since 

Your explanation is good though and refreshes some dim dark memories for me 

Honda's are in a similar predicament I believe, and their solution was to use the MOSFET type reg/rec's which share the same chunky Furukawa connectors as the SH775, but of course they're still shunt style, just beefier shunt style than the little GS type ones.

Before the SH775 came on the scene, the common fix over on the GSR was to put a Honda reg/rec on, SH532 I think was the preferred model, and I still have one of those in the cupboard here just in case.

[The Buddha]

I am still confused. I think that the difference between a generator and an alternator is that a generator puts out DC, so there is no rectifier needed. There are permanent magnet alternators and electromagnet alternators. The permanent magnet ones, like on the GS, put out more and more current (up to a certain amount) according to rpm's. The electromagnet alternators can be regulated by making the magnet stronger or weaker--the job of a regulator. Since the excess current of the GS is turned into heat, I am curious about two related   things:

1. How the current is re-routed back to the stater
2. If less current is used by LED bulbs, why isn't there more excess current that has to be turned into heat?

Thanks in advance for any clarification that can come into my foggy old mind.

Trying to explain what I can in simple terms.
Generator dont put out DC. Nothing except a battery puts out DC. I think generator is 2 phase, while alternator is 3 phase ? I better google this.

On a GS or on any bike with a permanent magnet, the current isn't routed back to stator. On bikes with alternators with electromagnets, when demand is high, it will increase the magnetism of the rotor and make more power from the alternator both as voltage and as current..

Less current used by LED's on a GS will result in the R/R getting hotter - except a GS consumes more in spark energy @ 5-6k and above than the alternator makes so the battery actually loses charge slowly. With less useage, you shift that threshold voltage higher and higher. If you ran without lights you could be making the battery charge to 8k. So its not going to be lost in more heat unless you're puttering along @ 5k all day.

The R/R still makes a lot of heat, but that's cos the alternator makes a lot higher voltage as well as more current when its revved higher and higher. So your gain isn't linear. as in 30 watt less useage not = to 30 watt charge to battery in the real world. You'd get 25 watt to battery and 5 as heat. No worry, the R/R usually wont be affected by that extra heat.

Now, having said all that, you could try one of those polaris or one of those schottky diode based R/R's. Those are better at turning 3 phase higher voltage alternating current to regulated DC of 14-15V very very well and making less heat, and getting rid of that heat very well.

Cool.
Buddha.

[The Buddha]

And -
In an alternator, electricity is produced when a magnetic field spins inside the stator (windings of wire).  = GS and XS650 and every other bike I know of. not to mention all cars I know of.
In a generator, on the other hand, the armature or windings of wire spin inside a fixed magnetic field to generate electricity. Please dont tell me a generator for my house has this - Cos I aint buying that crap then. Ever. Though I have one of these already.

Yea, distinction without a difference (unless you were a electrical engineer building these behemoths air turbines). Then you should get an alternator for it and forget about the generator anyway.

Cool.
Buddha.