Topic: '74 550 charging output 13.4v at 4000rpm. Good?

[orange550]

I've read some of the FAQ and I'm going to dig into my charging system, but I was just wondering on the broad strokes... I'm getting 13.4v at 4k rpm. That almost hits the "higher than 13.5 is ok" that I read about. But maybe I should really strive for say 14.5?

Or be happy with 13.4?

Thanks

[Deltarider]

How accurate is your meter? Digital meters can show funny results.
If true, it's a bit low. 14,3 V is ideal. 14,4 should be the maximum.

[TwoTired]

I've read some of the FAQ and I'm going to dig into my charging system, but I was just wondering on the broad strokes... I'm getting 13.4v at 4k rpm. That almost hits the "higher than 13.5 is ok" that I read about. But maybe I should really strive for say 14.5?

Or be happy with 13.4?

Thanks

Batteries don't charge or discharge instantaneously, which is primarily why they are useful, if you think about it.

Any good battery will show 13.4 volts at some time while on its way to being fully charged to 14.5V (at which point the Vreg should reduce current flow to the battery).  So, your absolute reading at a given point in time, without knowing battery charge status has rather limited value toward making an assessment.

All the charging system diagnostics begin with having a known good, fully charged battery, in order to characterize charging system performance at maintaining the battery at full charge status.

If you are going to evaluate your charging system, you may also wish to review the electrical load you are placing on it.  Common mods include higher wattage headlights and "super" coils/ignition components, which erode charging system reserve potential.

Cheers,

[orange550]

I've read some of the FAQ and I'm going to dig into my charging system, but I was just wondering on the broad strokes... I'm getting 13.4v at 4k rpm. That almost hits the "higher than 13.5 is ok" that I read about. But maybe I should really strive for say 14.5?

Or be happy with 13.4?

Thanks

Batteries don't charge or discharge instantaneously, which is primarily why they are useful, if you think about it.

Any good battery will show 13.4 volts at some time while on its way to being fully charged to 14.5V (at which point the Vreg should reduce current flow to the battery).  So, your absolute reading at a given point in time, without knowing battery charge status has rather limited value toward making an assessment.

All the charging system diagnostics begin with having a known good, fully charged battery, in order to characterize charging system performance at maintaining the battery at full charge status.

If you are going to evaluate your charging system, you may also wish to review the electrical load you are placing on it.  Common mods include higher wattage headlights and "super" coils/ignition components, which erode charging system reserve potential.

Cheers,

Forgive my ignorance, but am I not seeing the charging system output as I increase the RPMS? With my meter on the battery terminals, I increase rpms from 1k to 4k, my meter reading increases then levels off at 13.4v

[TwoTired]

Are you beginning the test with a fully charged battery?  How do you know?  What does it read before starting the bike?

Are the lights on or off?

Does the black wire at the Vreg read the same voltage as the Battery POS terminal?

Don't mean to be snide.  But, are you wanting to learn how it works/how to fix it, or do you just want someone to tell you what to replace?

Tell us what meter you are using.  If your Vreg is in "chatter" mode after fully charging the battery, you won't see 14.5v on an averaging meter.  And you may have to measure AC voltage on the Black or White wires, to calculate what the peak voltage the Vreg is deferring to.

Or, maybe you have a bad diode in the rectifier, or too much load placed on it.  Don't have enough data yet to make any judgments.
Have you done the ohms test to the rectifier?

Many mysteries vanish with knowledge gained.

[TwoTired]

I don't recommend tweaking the vreg, unless you really know what you are doing.  (Temporary bypassing is preferred.)  It doesn't behave in a fashion many conjecture it does.  Doing it wrong is easy for the untrained, but can result in a boiled, damaged battery during a longer ride, as the voltage trip/limiting protection is corrupted.

[orange550]

Are you beginning the test with a fully charged battery?  How do you know?  What does it read before starting the bike?

Are the lights on or off?

Does the black wire at the Vreg read the same voltage as the Battery POS terminal?

Don't mean to be snide.  But, are you wanting to learn how it works/how to fix it, or do you just want someone to tell you what to replace?

Tell us what meter you are using.  If your Vreg is in "chatter" mode after fully charging the battery, you won't see 14.5v on an averaging meter.  And you may have to measure AC voltage on the Black or White wires, to calculate what the peak voltage the Vreg is deferring to.

Or, maybe you have a bad diode in the rectifier, or too much load placed on it.  Don't have enough data yet to make any judgments.
Have you done the ohms test to the rectifier?

Many mysteries vanish with knowledge gained.

So I spent today working on the bike.

Bike info: 1974 CB550
5ohm Dyna coils, Dyna Ignition, new NGK plug caps, but the 5k ohms resistance ones. Non 'R' plugs, all other electric stock.

I initially had battery trouble when I was re-installing headlight and dashboard wires and lights. Was cleaning light sockets, etc and had the key on to check connections. I knew I should have recharged the battery, but I did a 75 mile back road ride. Lots of 4k/5k rpm riding. Figured that would at least enough charge  to not make battery worse.

The battery went downhill to the point it would not turn over the bike. Measured the charging when I got home. Was 13.4 at 4k rpm. Thought that was low.

Today I went through some things. My knowledge of electical is pretty basic.... Using a Sperry DM-350A. It Does V, A and resistance, etc... lots of decimal places.

Pulled rectifier.

Set tester at Circuit / resistance setting? It starts at 1.0 then goes to .000 when something has no resistance ??

Yellows to Red
.470, .464, .472 - reversed polarity. tester stayed at 1.0

Yellows to Green
.479, .480, .475 - reversed polarity. tester stayed at 1.0

Voltage regulator
with key on battery reads 12.12 / Vreg sees 11.6 (on the black lead)

Pulled Vreg - tested resistance
Black to White - 1.0 (no change on tester)
Black t0 Green - .035
Green to White - .035

Checked core gap - just under 1 mm / Points gap - .380 mm

Put a bit of emery paper thru points gap on Vreg. Cleaned all the plug connections in the 'panel'

Charged battery - 13.5V. After an hour or two it settled down to - 12.77V

1st - test - Running with lights on
Idle - 11.8
2k - 12.3
3k - 13.3
4k - 14.10

(however, after it was warmed up and I kept checking I never got it back to 14.1)

2nd - test after waiting a few minutes / running lights on
idle - 11.75
2k - 12.08
3k - 13.02
4k - 13.4

Turned running lights off

3k - 13.05 ish
4k - 13.67

When I turned the lights off and on during test. 4k rpm output would go from 13.6 ish to 12.6 ish

Also, when I increased the RPMS from idle to 4k plus, the volatge went up, but very slowly.

Turned off bike, battery read 13.3 - ish

Thoughts / questions:

- did the output drop on subsequent tests because the vreg saw that the 'need' was lower?
- I'm sure there are other things I should check?
- I wonder if the Dyna ignition is pulling just a little more power and is putting the bike in a deficit more often then normal.
- have considered unplugging the front signal running lights, but I like that added safety that other drivers will see me
- I still could go thru the bike and clean as many bullets as I can. maybe that would help.
- maybe my Vreg could actually use a very slight adjustment?
- should the voltage go up faster with higher RPMs or is it normal for it to creep up?
- or maybe these numbers are pretty good?

Any thoughts? Thanks!

[orange550]

If you count the screw turns on the regualtor that you make and note the direction you can always revert  to it's previous condition. Try it, the electrical engineers featured it for a reason. It's not like you are dealing with a magical device or something. I adjusted mine last year after a rebuild using the shop manual instructions. I checked the point/core gaps just like you did first to verify specs. If the battery is fully charged and the bike is warmed up then the voltage indicated is bascially what you see is what you get at the various rpm ranges. It's not rocket science. After that should you have no success I'd measure the load with an amp meter.

rt

Do you think my numbers are low given the info?

Thanks

[TwoTired]

1974 CB550
5ohm Dyna coils, Dyna Ignition, new NGK plug caps, but the 5k ohms resistance ones. Non 'R' plugs
all other electric stock.
Using a Sperry DM-350A.

Pulled rectifier.

Set tester at Circuit / resistance setting? It starts at 1.0 then goes to .000 when something has no resistance ??

Yellows to Red
.470, .464, .472 - reversed polarity. tester stayed at 1.0

Yellows to Green
.479, .480, .475 - reversed polarity. tester stayed at 1.0

Although the test show the rectifier in good health, for future reference you should use the diode function on your meter to check the rectifier diodes.

Voltage regulator
with key on battery reads 12.12 / Vreg sees 11.6 (on the black lead)

You should do this test again.  Once with lights on and once with lights off.  ( Suspect there is a bigger V drop with lights on and that low voltage is reducing alternator output power.)

Pulled Vreg - tested resistance
Black to White - 1.0 (no change on tester)

This is not good.  At rest unconnected, the white to black should read zero ohms.   An internal contact should rest with a solid connection between white and black, passing full battery power to the alternator field coil.

Charged battery - 13.5V. After an hour or two it settled down to - 12.77V

Your battery is reliable, imo.

1st - test - Running with lights on
Idle - 11.8
2k - 12.3
3k - 13.3
4k - 14.10

(however, after it was warmed up and I kept checking I never got it back to 14.1)

2nd - test after waiting a few minutes / running lights on
idle - 11.75
2k - 12.08
3k - 13.02
4k - 13.4

Turned running lights off

3k - 13.05 ish
4k - 13.67

When I turned the lights off and on during test. 4k rpm output would go from 13.6 ish to 12.6 ish

This could indicate a lossy voltage path between battery and field coil input, which would diminish alternator output capability.
At the 4k or 5K RPM measurement, I would like to see an AC measurement between the white and green wires attached to the vreg. (To see if the Vreg is "chattering" or hunting to maintain battery full.)

Also, when I increased the RPMS from idle to 4k plus, the volatge went up, but very slowly.

The battery drains anytime the bikes power demand exceeds alternator output.  Normally with lights on the stock bike draws about 120 watts (yours will draw more because of the Dyna ignition trigger).
At idle and with full battery voltage applied to the field coil, the alternator only makes 40-50 watts, which causes the battery to loose energy making up the difference.  By 2500RPM though, the alternator should make enough power to not only run the bike, but begin to restore lost power to the battery, and the voltage should slowly rise.  However, the alternator can't even make 40 watts at idle if the white wire field coil voltage is less than 12V.

Turned off bike, battery read 13.3 - ish

 
This is a surcharge potential from a recently recharged battery, indicating it is full.

Thoughts / questions:

- did the output drop on subsequent tests because the vreg saw that the 'need' was lower?

I'm not yet convinced the Vreg is seeing an accurate report of actual battery voltage.  Do the tests noted later, so we can eliminate component failures, allowing concentration on power distribution matters.

- I wonder if the Dyna ignition is pulling just a little more power and is putting the bike in a deficit more often then normal.

Yes.  It leaves the coils pulling power about 60% more than points do.

- have considered unplugging the front signal running lights, but I like that added safety that other drivers will see me
- I still could go thru the bike and clean as many bullets as I can. maybe that would help.

It may well.  You may also need to rebuild the key switch, and block connectors as well.

- maybe my Vreg could actually use a very slight adjustment?

I won't eliminate that as a possibility.  But, there is no smoking gun to say that is required, yet.

- should the voltage go up faster with higher RPMs or is it normal for it to creep up?

Creeping is normal.  The charge voltage goes up with the rate of current input.    More current/ the faster the rise.  Remember that the bike steals current from the alternator before the battery can receive any excess.  So, there is only 1 or 2 amps available to deliver to a 12 ah battery.  At that rate, a depleted battery will take 10-ish hours to fully charge.

- or maybe these numbers are pretty good?

I don't think so.  I'd guess you have power distribution losses, at this point.  But, some more testing will point the way for effective corrective action.

Any thoughts? [/quote]
I'd like to see this:

Remove the white wire from the Vreg and measure resistance between the white wire and the green wire.  This is the field coil winding and should be 4.9Ω -ish
If this is nearly correct.  Then make a temporary jumper wire that connects the white wire directly to the battery POS terminal.

Start the bike and note the voltages at idle, 2000, 3000, 4000, and 5000 RPM.
Repeat this test with the lights on.  However, if the battery voltage ever rises to 15V, curtail the test, and note the RPM/time where it occurred.

[TwoTired]

This is a cross post.  You may have read the following elsewhere.

The SOHC4's regulator isn't a direct system output stabilizer.  That is actually the job of the battery, whose charge status dominates what the system voltage is.
The regulator's only direct job is to maintain battery health.  It's only means of accomplishing this is to tell the alternator to reduce it's power output when the battery is full.  At all other times the alternator is allowed to be-all-it-can-be, do-all-it-can-do.

Three factors determine alternator output strength; one is designed in, as the stator coil's wire size and number of "coils". This determines its maximum output capability.  The other two factors are RPM, and the voltage applied to the field coil, which determines the magnetic field strength that the alternator needs to induce current and voltage in the stator windings.

The "regulator's" black wire input serves two purposes.  One is to obtain a sense of what the battery voltage actually is.  And, the other is to pass the power received on that black wire to the White wire terminal, when the alternator needs to generate power.
The regulator cannot pass more voltage/power to the alternator field than what is receives.  If it receives low voltage, the alternator will remain weak despite sensing that the battery "needs" more power for recharge.

For this reason, making any regulator adjustment as the first attempt toward corrective action is almost certainly a mistake.
It is only after all the other components of the charging system are checked/verified, and only after checks of black wire voltage loss/misrepresentation of true battery voltage errors are known and eliminated, that the "fine tuning" of the Voltage regulator be examined and adjusted if necessary.  (And then, only under the conditions of the battery being full and the alternator known to making more power than the needs of the bike and battery combined.)
For a 30+ year old motorcycle, it is quite unlikely that all the rest of the system components, switches, wiring connectors, etc, are still operating at "as new" specification.  The regulator is not a tool to compensate for other faults/irregularities.  Just because it is the "easiest thing to meddle with, does not make it the "go to" first thing to alter in a troubleshooting scenario.

Most times it is better to look before leaping.

Here is the bad scenario:
Vreg is "tweaked" in an attempt to raise battery charging.  May even have temporarily "helped"
True cause was lost voltage in the power distribution from battery to Vreg.  For this example, we'll say it was the ignition switch losing the voltage.
Later the switch fails outright and is replaced.  The earlier charging system problem is forgotten, as well as the memory of the vreg tweaking, which in fact raised the max battery charging voltage cut off point.  On a subsquent long cruise, the battery gets overcharged, "boiled out", and damaged.  Could be stranded, could cost a new battery (or several) until the vreg gets properly adjusted, and the meddler (or bike purchaser) buys a new "electronic" regulator to solve the tweak problem induced way back when it wasn't understood what changing the Vreg adjustment actually meant.  To me, that's a lot of money spent in the aftermath of an errant and ignorant vreg tweak, that I'd personally rather spend somewhere else.

Perhaps this post will save you some money, too.  And, keep your trip riding at full enjoyment level.

Cheers,