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Discussion Starter #1 (Edited)
I'm wondering at what voltage I should start to worry about too high an output from the alternator, causing damage to Radio, CB, Lighting and other electronics?


I have a 1999 GL1500 with a Comp-U_Fire 90 amp output alternator. The alternator was installed about 10 years ago. I'm using an AGM battery that is about 5 years old. The battery has been load tested and found to be in good (Acceptable) range. The bike when parked has a Battery Tender Plus attached to keep the battery fully charged.


My experience over the years has been the Air Rider Digital Shift Indicator/Volt Meter reads about 14.2 to 14.3 volts output from the alternator. On rare occasions it may read as high as 14.5 volts, but only very briefly. The bikes volt meter has been verified correct/ accurate with 2 other quality DVMs.



I am now seeing when I start the bike that the alternator output is 15.0 to 15.1 volts. Even at Idle. Eventually after riding it it settles back to 14.2 to 14.3 volts. I have never, (in past years) seen the alternator output that high.


I have read in posts that the service manual states that 15.1 is acceptable, but also read in posts that the Honda Service Manual is not always correct and they disagree with that high an output voltage.


What are your thoughts? Has the voltage regulator started to breakdown and put out too high a output voltage, that would be damaging to the bike. Could the battery test OK, but actually be in need of the high charge level?


I'm looking for a little help on this one. Thanks, DJ
 

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Discussion Starter #2
Follow up Question: If my battery was in need of a charge after being taken off the Battery Tender Plus and started, shouldn't the Alternator voltage regulator limit its output at about 14.5 volts and just take longer to top off the battery.


I have also swapped out to a different Battery Tender to see if it made a difference. No change.


Thanks, DJ
 

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15.1 is a bit too high if it lasts for very long, a couple of minutes would be okay.
the regulator should drop to 14.3-14.4 very soon after engine starts up cold.


once the engine is warm, and the battery has equalized to about the same temperature, the voltage should drop to 13.6-13.8


my 1800 however, stays at 14.1 all the time which is a tad bit high, but I am not going to try and fix what is not really broken. been that way for years, going to leave it alone.


If the battery turns the engine over fast, and it starts while pushing the starter button, the battery is okay.


If, it won't actually start until you release the starter button, then I suggest that you get a new AGM battery.


A good battery will hold the charging voltage down where it should be normally.
but, with a 90 amp alternator, it is really going to depend on the regulator working properly.


I have gone back and read both of your posts, and want to agree with Dennis.
I think it is time for a new battery.....
I would save the one you have to use for hobby stuff.


as for the CB and other electronics, they will survive continuous voltages up about 16 volts..... but, I would not be comfortable at that level if it were mine.


My thoughts are, if it stays at the 15.1 level for more than a couple of minutes, a new battery is needed.


The battery should always be topped off completely with a Battery Tender on it, it will not need to be heavily charged...
however, my battery tender seems to stay at around 13.6-13.8 on my 1800.


on my RV which has a 1,000 CCA Deep Cycle Marine battery, that Battery Tender seems to stay at about 12.8-12.9
 

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I would check the charging voltage using a quality voltage meter connected to the battery terminals. 14.5 volts is about right. A steady 15 volts isn't right. Maybe a visit to the auto-electrician to check using their equipment would put you at ease.
 

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I really suspect your meter is reading high, and...

the battery is getting old so it loses a bit more juice when it cranks, so...

the charging system pumps out a bit more juice (½~¾ volt) to top it off, then settles back to what is normal for that meter.

So, again, the battery is going.

5 years is a good run for a motorcycle battery.
 

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My 1800 starts out at 14.7-14.8 cold then settles down to 14.4-14.5, yours isn't far from that.
 

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Discussion Starter #8
I really suspect your meter is reading high, and...

the battery is getting old so it loses a bit more juice when it cranks, so...

Dennis, I do agree with you that I'm also leaning toward the battery. It does start up fine, and does so very quickly with full choke. That's why I was putting off replacing the battery.


My bigger concern was with the 15.0 to 15.1 volt output causing damage to electrical components. I'm not sure how much voltage is too much for the Radio, CB, Garmin GPS or other bike components with short term high output from the alternator.



I disagree with it being the meter reading being HIGH though. The on bike meter has now been verified with 3 different digital voltmeters, two of them being known good, high end, Fluke meters. The readings have only varied by .1 to .2 volts from the meter on the bike.
 

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My bigger concern was with the 15.0 to 15.1 volt output causing damage to electrical components. I'm not sure how much voltage is too much for the Radio, CB, Garmin GPS or other bike components with short term high output from the alternator.
.

as I already said, if it never goes above 15.1 you have nothing to worry about.


the radios and electronics will be just fine.


15.1 is only 0.7 volts higher than normal anyway


most electronics stuff can handle 100% overload for a short while.
 

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Automotive electronics are spec'd "nominally" at 13.8V (14 really) and not 12 volts, so you are only 1.3 volts over when reading 15.1 volts. Sensitive low voltage internal circuits will have built-in voltage regulation which is necessary because the input voltage can vary so much. Your electronics will tolerate up to 17 volts all day long.... and if your voltage is THAT high you DO have a problem.
 

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First thing I would check is for voltage drops across all connections between battery, alternator, and ground. No connection should produce more than .1 (one tenth) of a volt drop. Ideally voltage should be the same everywhere in the circuit.
If that checks OK, I would think that the battery is degrading, Your voltage reading is dependent on the load placed on the alternator. In an older battery, repeated charging and discharging produces a coating on the plates, and this reduces the ability to accept a charge. It becomes more of a Capacitor than a power/load source. Also AGM batteries have different charging needs.
I am not familiar with your alternator setup, single wire or second lead to regulator? If single wire, probably no problem. If it has second wire, then again, connections are important.
A 90 amp alternator is a large output value for a motorcycle battery, but that amperage is only realized as loads from accessories, lights, and ignition are placed in the circuit.
After starting, the battery is briefly in a discharged state. At that point, it's voltage is lower than the alternator voltage. It is presenting a "load", once the battery voltage equals the alternator voltage, and that voltage is equal to the regulated voltage, all charging should taper off. 14.2 volts is all that is needed to satisfy a healthy battery. Very small resistances in the charging circuit can cause the "load" to be false, allowing the voltage to rise.

Before the days of electronics, some mechanics would start the engine, then disconnect the battery, if the engine died, then they assumed the alternator was bad. This is not a good thing for electronic circuits because if the alternator is OK, it's output voltage will run "wild" because of lack of load from that battery. Using the electronic circuits a load, for voltages >16 volts.
Does your motorcycle have a tendency to drain the battery when not running? I ask this because you said you have a battery tender. Some are good, others only amount to a 1 amp continuous charger, with no regulation. This promotes the "plate coating" I spoke of earlier. A proper tender should be active, shut off at a given voltage, turn on a given voltage. 12.7-14.2.
 

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Discussion Starter #12
Does your motorcycle have a tendency to drain the battery when not running? I ask this because you said you have a battery tender. Some are good, others only amount to a 1 amp continuous charger, with no regulation. This promotes the "plate coating" I spoke of earlier. A proper tender should be active, shut off at a given voltage, turn on a given voltage. 12.7-14.2.

I guess the short answer would be YES. The bike will sit from November to the end of March, so I'm sure that there would be some battery drain. That is why the "Battery Tender Plus". It has done a great job over the years to keep all of my batteries fresh. I actually have four various models of "Battery Tenders" in use on different bikes or tractors throughout the year. And yes they do regulate the charge cycle.


http://products.batterytender.com/Chargers/Battery-TenderR-Plus.html


As for the connections, I will go back and check for loose or oxidized connections, just to be sure. I am leaning toward the battery starting to fail, although it does currently turnover and start the bike quite well.



It just seems the battery draws more of a charge at startup than I would think the internal regulator should be putting out. I kind of expected the voltage regulator to limit the output to somewhere around 14.5 to 14.8 volts max. Maybe it's just me thinking the output voltage should be lower than the initial 15.1 volts. That is based on the years of seeing my output voltage hovering around 14.1 to 14.3 volts continually.


Thanks for you input, DJ
 

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Discussion Starter #14
I'm thinking that 15.1 is erroneous.


use a high quality DVM and verify what you are seeing measured across the battery terminals.

AZ if you don't mind my asking what do you consider being a high quality DVM. I may have to track something different down. I have used Fluke DVM's across the batteey. I thought that they would give me an accurate reading.


I realize it is mainly used to measure AC and frequencies but, it will also measure DC voltage. I'm am about to break out the RIGOL oscilloscope to see if I get a different reading with it across the battery.


Would like to get to the bottom of this issue...


Thanks, DJ
 

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I would say battery on it's way out. 5 years is the most I have gotten out of a good quality sealed battery. It just sound like the battery is demanding more power to charge because it is on it's way out.
 

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.


The on bike meter has now been verified with 3 different digital voltmeters, two of them being known good, high end, Fluke meters. The readings have only varied by .1 to .2 volts from the meter on the bike.
I'm thinking that 15.1 is erroneous.


use a high quality DVM and verify what you are seeing measured across the battery terminals.
Flukes are pretty good meters John.
 

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Fluke meters are one of my standards in the industry, I don't recall the brand being mentioned in this thread. if it has, I overlooked it.



but, even the el cheapo DVM sold by Harbor Freight is pretty darn close. I have one of those, and it reads real close to my Fluke


by "quality", that means an instrument of known calibration that reads consistently.
 

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I'm sure you have another 12V battery (car, truck, riding mower....), why not disconnect the bike battery and jumper in another for test? Then you will know if it's the battery or the bike.
 

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One thing you could try to confirm suspicions about battery, would be to hook up another battery with jumpers and then check charging voltage. If your present battery is rejecting charge, then the addition of the second should drop the voltage. All alternators produce AC before it is rectified to DC. In the process, the negative pulse of the AC wave is clipped off at the 0 volt line. The alternator has 3 phases, each phase is 120 degrees later than the last. The phases fill in the timeline with only the positive pulses, since the negative one are blocked by the diodes. This would be seen as a series of Camel hump shaped pulses all slightly overlaid (delayed) in time. The peak voltage would be higher than the average( the point were all the lines cross). The load that the battery presents to the alternator tends to pull the peak voltage closer to the average. A battery that has developed a coating on the plates cannot except voltage as a charge. That is what I meant earlier when I said it acts more like a capacitor than a battery.

I think if you had an ammeter in the circuit, you would see a higher voltage with a lower amperage.
 

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All alternators produce AC before it is rectified to DC. In the process, the negative pulse of the AC wave is clipped off at the 0 volt line. The alternator has 3 phases, each phase is 120 degrees later than the last.
Nope, The rectifier is a three phase bridge, all of the three phase AC (including the negative-going part of the sine wave) is used in making DC! Very efficient! :smile2:

None of the three legs of the alternator go negative with respect to the Bike's ground because there's no ground reference anywhere in the alternator, even the common point of the three phases floats. Thus the negative-going part of the sine wave is referenced to bike's ground thru the negative-rail diodes in the bridge, thus driving the positive-going legs to an even higher output.
 
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