Topic: CB550 K1 - standard charging behaviour?

[Erny]

Reading many posts here about relatively low power of standard CB550 alternators and linked issues with charging / higher power headlight etc, I installed V-meter to monitor charging on my 550, especially after I changed headlight insert from sealed beam to modern H4.

What I realised is that with lights on, alternator is charging (depending battery charge status), usually I see more than 13V from 3000 RPM up) but noticed strange behaviour on higher RPMs. When engine revs (typically if I ride faster, higher speeds) over 5500-6000 suddenly voltage drops by approx 0.6-0.7V. So for example till 5500 voltages is about 13.5V and then over 5500 it drops to 12.8V. When revs are back under 5500 it goes up again.
Looks to be that regulator relay is switching off field coil (reducing current via field coil) but looks strange to keep so low voltage...

Is that behaviour normal? Or shall I check/adjust regulator?

V-meter as instaled on the attached photo


Note: when I switch off lights voltage goes up to more than 14V, but I did not tested yet behaviour on higher RPM w/o light.

My setup:
- V-meter is connected to headlight (green and black terminal), it measures correctly (+/- 0.1V compare to my precise mulitimeter). There is obviously some voltage drop comaparing batt voltage and voltage in headlight but this is not important I assume
- Black terminals in headlight shell are fed via relay directly connected to battery + terminal via fuse. Relay is controlled by ign switch to offload switch itself
- when I swapped sealed beam headlight to H4 insert, I disconnected position lights in front side indicators (2x 8W) as H4 insert has position bulb inside (4W). I also have low cons LED bulb in taillight and rear indicators. All in all this headlight swap shall be +/- energy neutral considering load added vs removed.

[bryanj]

Somewhere on this site is a Honda bulletin that explains the 3 phase charging system, basically the reg fluctuates between no charge, approx 1/2 charge and full charge depending on battery voltage. As its mechanical vibration can affect it as can corrosion, old age, volt drops on connevtors etc etc

[Erny]

This I understand, but question is of drop I'm observing in higher rpms is normal or not (I don't think so)

[bryanj]

Probably not but never tested that way, is probably due to mechanics of the reg with age and vibs making it "float"

[maxheadflow]

BryanJ is right on and you are correct the voltage should not drop.  While you definitely want to go through the connections with a bike of this age, regulator vibes can be an issue.  It was an issue back when the 550s were new.   Make sure all your connections are clean even the ones going to the rectifier.   Loose connection on the rectifier can blow it. It was a common issue for the bikes back then to blow rectifiers when water got into the connectors and corroded them. My 76 cb550f blew a rectifier that way. I'd fixed others that had done it.  Another issue is one of the alternator windings shorting to ground due to a loose coil / wire.  Vibes can cause an intermittent short.

[TwoTired]

I suggest you verify the voltage drop between Battery and voltage regulator, both the black wire connection and the green, before messing with the regulator.
 
Stay off the "adjuster" as most don't understand what it does or how set it properly.  It is to set the max limit of voltage allowed at the battery, where it then tells the alternator to back off a bit so the battery can't "boil".  It is critical that the Vreg get an accurate report of true battery status, or it can't do it's job.  It doesn't really regulate system voltage, other than to keep the battery healthy.  That is the system regulation, battery status.

Ign switch contacts can become marginal and vibration can make them worse.  This will drop voltage to the black wires, as can fuse box and other system connections and it can vary with the load (lighting placed upon it).  Basic ohms law.  E=IxR  Increase resistance or current, the voltage reduces.

The switch and connector losses can make headlights dimmer, as less voltage to headlight makes that dimming inevitable.  Drawing more current in a faulty distribution system will just make dimming worse.

You can easily check for distribution losses directly with a voltmeter.  One probe on Battery POS the other on the vreg black.  The loss will display directly.  Turn lighting on and off and you can see more loss with lighting on.  Don't forget the green to Batt NEG path, as it can have losses also, load dependent.  Sum the worst case measurement, and if you see more than 0.5V loss, something needs repair.

Cheers,

[Erny]

Thanks for the feedback.

All contacts are clean, w/o corrosion or oxidation, I did check all of them one by one when I did bike inspection few months back. Stator coils are also OK based on static (resistance) measurement with multimeter.

I'll do check of losses on black and green wire and report here (when I'm back from short holidays)

Good at least you confirmed to me that such drop is not OK (as I expected)

I can eventually swap for short time regulator from my 750 K7 & test, is that the same? It looks to be...

[Deltarider]

Erny, what is the problem you have, apart from some aftermarket voltmeter that you have fitted, giving strange readings? And why the relay? Is it sound?

[Erny]

No spefific pb apart of big voltage drop on high RPMs. At least this is what I see as an issues.
Maybe I'm just too senstive (as electrician) to charging issues...but had many issues with other old bikes that always suffered from low power.

I want to be sure charging works as should,  so bike is reliable to ride longer distances/trips w/o being afrraid to get stuck somewhere on the road out of battery

And relay - I found quite big voltage drops between bat POS and headlight terminal on bulb so wanted to reduce it and offload ign switch, especially knowing I'll install H4 bulb

[Deltarider]

No spefific pb apart of big voltage drop on high RPMs.

Did you doublecheck with another voltmeter? Or - in other words - does the headlight dim on high RPMs? Other than you will read in this forum, the charging system of these Honda's has quite a good reputation, at least here (in Europe). As far as the electric system, there are just a few things that may need attention. Main fuse and fuseholder is one. They should be clean and free of even the slightest corrosion. Where the wires of the generator exit the left sprocket cover (upwards) is a spot where some chafing can occur. For the rest the system is rock solid. So check and doublecheck carefully whatever you have fitted as an extra afterwards.
BTW, I myself was never lucky with digital volt reading on my bike. Voltages went all over the place. But then I realised: all my batteries lived long, every ride I return with a better charged battery than I took of with, the battery doesn't gas abnormally and the system doesn't blow bulbs. So I concluded I don't have a problem and if I don't have a problem I certainly will not look for one. As my bike already came with an H4, I never bothered to fit a relay. The only relay I have fit, was for the Voxbell horns (15A). I never bothered to monitor the charging. I have made it a habbit to, whenever I take of and have to wait at the first traffic light, I rev the engine and watch what the reflection of my headlight does on the van or truck right in front of me. That's my system.
 

[TwoTired]

And relay - I found quite big voltage drops between bat POS and headlight terminal on bulb so wanted to reduce it and offload ign switch, especially knowing I'll install H4 bulb

That is big evidence that something in your bike's wiring, connectors, switches, or fuse box is wonky.  The relay only bypasses the problem, not a cure.

Cheers,

[strynboen]

think it are normal that the generator goes flat..at heigh rpm..have worked 10 years at a elektro rep shop..and seen that many elektric motors..anf generators..Loose some  power..,, at heigher rpm then it are deseined to run...thosed generators vitaut a voltage kontroled autput..dont have a spec miniun/max kontroll..but are tunet to hold a balanced autput..vith some spikes both at low and heih end of spectrum

you can build inn  a bosch unit..so the voltage peak gets at 14,5 volt maxium...but dont think it make any difference at the power autputs in total..

[Erny]

And relay - I found quite big voltage drops between bat POS and headlight terminal on bulb so wanted to reduce it and offload ign switch, especially knowing I'll install H4 bulb

That is big evidence that something in your bike's wiring, connectors, switches, or fuse box is wonky.  The relay only bypasses the problem, not a cure.

Cheers,

Fuse box itself (contacts at terminals are clean) is something I did not check deeply, that's true... Will do so. Or, like on my K7 750 will replace by modern box with blade fuses to eliminate issue

[HondaMan]

Maybe pull off the cover of the regulator and check/clean the upper contact. If marginally dirty/pitted, vibes can make it drop connection, too.

[Erny]

Will check for sure too

[TwoTired]

And relay - I found quite big voltage drops between bat POS and headlight terminal on bulb so wanted to reduce it and offload ign switch, especially knowing I'll install H4 bulb

That is big evidence that something in your bike's wiring, connectors, switches, or fuse box is wonky.  The relay only bypasses the problem, not a cure.

Cheers,

Fuse box itself (contacts at terminals are clean) is something I did not check deeply, that's true... Will do so. Or, like on my K7 750 will replace by modern box with blade fuses to eliminate issue

The only reason why black wire voltage drops with increased current load is series resistance in the pathway.  While all conductors have some resistance as one of their properties,  connections in the pathway can become increasingly resistive as they oxidize, lose contact mating pressure, or area of contact.  Switches can become resistors and lose voltage, too.

Cheers,

[Erny]

That is clear to me also. I did check of all connectors and terminals, except deep check of fuse box. Loss is of course on all of them. That's why I opted for relay to eliminate it.
But still here is point is drop of voltage in high RPMs only.
I'll redo all checks once again, incl fuse box and regulator (will test swap from my K7 750 too)

[TwoTired]

But still here is point is drop of voltage in high RPMs only.

With RPM comes vibration and frequency.  One scenario, is that a switch contact (or other contact) loses contact area when it gets into a specific vibration frequency.  A worn contact, or one with poor spring tension could conceivably degrade under such conditions. 

...Possibly...  I've seen stranger things.

Cheers,