Battery Voltage

Honda Pan-European 1st generation (German design)

Battery Voltage

Postby Baldeagle » 28 Sep 2014, 12:18

Hi Folks,
This has probably been asked before, but are the following readings within normal parameters?

No lights=14.6
Side lights=14.8
All lights=15.6

All taken at 2000rpm

The bike is a 1990 1100 with 28 amp alternator,fully charged battery and new regulator/rectifier

Tried all the tests in the manual and all seems ok!

Thanks in advance, all advice welcome.

Bill
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Re: Battery Voltage

Postby mbrST1100 » 28 Sep 2014, 12:31

According to the manual it should not exceed 15.0V @ 5000rpm...
So 15.6V @ 2000 seem a tad high...
Any chance your multimeter is off? (low batteries, not calibrated to zero, etc...)
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Re: Battery Voltage

Postby Baldeagle » 28 Sep 2014, 12:51

The voltmeter on bike gives the same readings as multimeter.
Will put new batteries in multimeter just to be on the safe side.

Hate electrics!!

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Re: Battery Voltage

Postby David W » 30 Sep 2014, 02:50

What does the Honda manual say about test conditions? Going from memory, all lights should be off, and 14.5 volts seems normal to me for that condition; I have used that same test before. (And I predict it will stay near that value when Bill revs it up to 5000 rpm with the lights off.)

But that still does not really explain why the voltage should go up over 15 volts when the lights are on. The main problem with high voltage is that things like light bulbs burn out; so Bill should report any such problems here. (Maybe the higher voltage results from where he positions his test leads; current is flowing when the lights are on.)
mbrST1100 wrote:According to the manual it should not exceed 15.0V @ 5000rpm....
I think the Honda ST1100 service manual specifies all electrics off when taking the reading.
So 14.5 volts in that condition looks quite normal to me.
Baldeagle wrote:The bike is a 1990 1100 with ... fully charged battery and new regulator/rectifier.
Tried all the tests in the manual and all seems ok! ...
Bill
He's done the right thing with his battery; and the new, stock regulator/rectifier was probably overkill; so I would generally agree with Bill that all seems ok.
Just make sure all the lights work; keep the old regulator as a spare; then ride/ride/ride?
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Re: Battery Voltage

Postby Baldeagle » 30 Sep 2014, 20:28

The reason for the new rectifier was that the previous one was fried by the high voltage.
The test leads were placed directly on the battery terminals to get the readings.
I still don't think over 15volts at 2000 rpm is normal with lights on, surely it should not go above 15volts?
Did a repeat check on all wires going to the rectifier and all checked out as per the manual again,but rectifier readings were weird.
I am thinking about getting it checked at an electrical factors and see what they say.

Keep the comments coming folks.

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Re: Battery Voltage

Postby David W » 03 Oct 2014, 02:55

Bill, do you have a way to clamp or fasten the test leads in place, such as alligator clips slipped over the pointed ends?
That would assure that all voltages can be compared.

Both the old and the new rectifiers are the OEM type, right? The only way I've seen them fail is for the white plastic at the bottom connector to overheat.
Baldeagle wrote:The reason for the new rectifier was that the previous one was fried by the high voltage.
...
I still don't think over 15 volts at 2000 rpm is normal with lights on; surely it should not go above 15 volts?
Did a repeat check on all wires going to the rectifier and all checked out as per the manual again,but rectifier readings were weird.
... Bill

If the old rectifier was fried, do you means the spade terminals at its bottom overheated?
And if so, the white, plastic connector was probably damaged; and maybe one of the "female" terminals inside that connector was burned, too. (I once took all those wires loose from the white plastic, and replaced the plastic casing.)

The main, overall test is that the battery voltage, with no lights, should be between 14 and 15 volts all the way to 5000 rpm; 14.5 to 15 volts should be a good range. We have no specification for voltage with the lights on. Make sure that nothing changes when you simply turn on the lights to check that effect on voltage.

If you are trying to check the rectifier off the bike by taking resistance measurements on it, you will need an analog or non-digital meter for that, and what counts is the relative resistances because you do not have the same analog meter that Honda uses.

You have not noticed any unusually bright light bulbs? (They tend to burn out faster than normal.)

All,
Can someone else please check the effect of lights on battery voltage with the engine running?
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Re: Battery Voltage

Postby Baldeagle » 03 Oct 2014, 10:52

The present rectifier is OEM,but the previous one was aftermarket.
The white plastic connector, and the 3p connector from the alternator, were ditched a while ago in favour of the wires connected directly to the rectifier,so doesn't apply.
The black type sealant? on the back of the aftermarket rectifier got so hot as to actually melt onto the footrest hanger!!
The test leads were secured on the battery for all readings.
The rectifier will be taken to be checked out by an electrical expert when I can get time.(bit of family crisis at the moment :-))
The lights do seem to be slightly brighter than normal!! They get brighter with an increase in RPM,don't know if this is normal as I haven't noticed it before.
I agree 14-15 volts with no lights is good, would be interested to hear if anyone checks their voltages as per your request.

Thanks for the input.
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Re: Battery Voltage

Postby mbrST1100 » 03 Oct 2014, 13:27

David W wrote:I think the Honda ST1100 service manual specifies all electrics off when taking the reading.
So 14.5 volts in that condition looks quite normal to me.

Which is why his reading of 15.6V with lights on do cause a raised eyebrow here... so do brighter as normal headlights...
The system should not exceed <15V ever, as such would cook the battery (and blow the bulb filaments prematurely)...

My old '94 (fully overhauled, new stator, wiring top notch) gives like:
<13V @ idle (1000~1100rpm), lights off
<12V @ idle (1000~1100rpm), lights ON (2x 55W H4 + 1x 5W pos light + 2x 5W running lights + instrument illu), slight flicker of the lights, when hitting the hazard-flashers the finger of the voltmeter bounces between ~11 and <12V with the interval of the 4x 21W going on/off
under revs (= anything above 1500rpm), regardless of lights are on or off, the voltmeter settles steady at ~14.5V; under no condition do I see anything close to or over 15V...
(readings from the OEM P-spec onboard voltmeter)

The OEM VRR gets warm to the touch but not burning hot (so I guess ~40°C), and was installed with some white thermal compound paste (CPU cooler paste) applied to its contact patch at the footrest plate.
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Re: Battery Voltage

Postby Pieter Huizinga » 03 Oct 2014, 15:51

With my - admittedly limited - knowledge of electricity, I can't think of any reason for the voltage to go UP when the load increases (by switching the lights on). As Martin illustrates in his post above, it should go DOWN. Assuming all other things equal.

If you're not making some sort of mistake measuring, there is some serious shit wrong there.
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Re: Battery Voltage

Postby David W » 03 Oct 2014, 22:48

Must make this post brief:

1. A high voltage would not, I think, cook the battery; it will just charge the battery faster.
The reason high voltage must be avoided is to keep light bulbs and other devices from being subjected to higher voltage than they are designed to be subjected to.

2. The other way a rectifier can heat up is normal. Its back is metal side is designed to take heat away from the inside of the rectifier and transfer it to the metal "peg holder" that it is mounted to. The metal to metal contact should be as clean and direct as possible. Some people augment that interface with a paste that is variously called:
heat sink grease
heat sink compound
thermal grease or
thermal compound.
It is as carried by electronics supply, including computer supply stores.

Without further info on how the old rectifier was "fried", I cannot do much more to prevent the same happening to the new one. (I've described two ways for overheating. Was it the spade contacts, or the back plate that got too hot?)

3. The battery is by far the weakest link here. It may be time to give some details on it, like its age and country of origin.

4. A rectifier is involved here with controlling the battery voltage; maybe it is designed to up that voltage so that the battery keeps charging when the lights are turned on. The stock rectifier is pretty reliable.
So, based on having no time yet to read Martin's post, I've yet to see evidence of "serious shit" happening here.

5. Tracing the wiring back from the rectifier leads to a red, three wire connector, and a black, two wire one. The black one is "weather-proof" but is suspect here because it is how the rectifier "talks to" the alternator to control the alternator output, as I understand it. Both the red and the black one can be removed from its mounting clip with a flat-bladed screwdriver, to make it easier to inspect them for corrosion, or overheating (which is more likely with the red one than the black).
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