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Old 08-07-2020, 23:23   #1
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Voltage to spikes voltage

My alternator voltage puts out over 15 volts of power after it has been running for a while. The voltage starts out about right at around 13.6, But after the motor runs for a while it spikes up to over 15 volts. It stays there for a while then goes back to around 14 volts. Then is cycles back up to high voltage and back to normal voltage. The voltage fluctuates over time. What might be causing this issue? I've cleaned all the negative terminals as well has have cleaned off all the terminals. Any idea what might be causing this voltage fluctuations over time?
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Old 09-07-2020, 01:30   #2
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Re: Voltage to spikes voltage

Sounds like the voltage regulator on the alternator has gone bad.
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Old 09-07-2020, 05:08   #3
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Re: Voltage to spikes voltage

Yeah, it does sound like the regulator. The voltage that you are reading is the charge to the batteries. If you've got dead batteries, that voltage coming of the alternator will read about 11 volts, and climb to 14 or so with a working regulator. When you shut down, flooded batteries will drop to a resting voltage of 12.8.

With the heavy cycling load that we put on house batteries, a sophisticated voltage regulator like the Balmar is a worthwhile investment. I use crude single wire alternators for the start batteries for the main engine and the genset - all they do is supply starters for a few seconds and then have lots of time in which to recover. For the house bank, it's a high amperage Balmar alternator and a Balmar voltage regulator that emulates the sophisticated battery charger that runs off shore or genset AC.

Be sure that the alternators are big enough. A 90 amp alternator that is required to supply 90 amps to a big house battery bank will be toast very quickly. They overheat and die a horrid death running their little hearts out.

Good luck with it.
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Old 09-07-2020, 06:19   #4
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Re: Voltage to spikes voltage

Sounds to me that it’s set point is 15V but keeps getting set back from overheating.
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Old 09-07-2020, 08:30   #5
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Re: Voltage to spikes voltage

I am assuming you are getting your voltage readings from an analog engine panel voltmeter. The first thing to do is confirm the accuracy of the voltmeter with a handheld digital voltmeter. If the panel meter is correct the problem is the voltage regulator.
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Old 09-07-2020, 10:20   #6
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Re: Voltage to spikes voltage

I have the same problem. I have a year-old Balmar 125amp alternator and ARS-5 Balmar regulator, and after installing 3 Firefly carbon foam batteries I thought I had a bulletproof setup...but on startup I'll always show 15.4 volts on the battery monitor. And at the battery. And, more importantly, on the ARS-5 readout itself. The Cv voltage, the target bulk charge voltage, as read on the regulator, is the correct 14.4, as I programmed. So this is a deeper mystery than first thought. Many calls with Balmar tech support later, I'm led to believe the high voltage is due to a surface charge. It's true that if my house bank is down a ways, the regulator will bulk at 14.4...but for no reason it will flip back up to 15.4 at some point, and then back and forth randomly. The regulator just will not control it. Tech Support said one solution (that "another boat is doing successfully") is to put a switch in the brown ignition wire (it's in the harness) to "turn off" the alternator while things are acting up like this. No harm to the alternator. We don't want to fry our batteries...if you or anyone have more theories on this, I'm all ears.
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Old 09-07-2020, 13:24   #7
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Re: Voltage to spikes voltage

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Originally Posted by Poeme View Post
I have the same problem. I have a year-old Balmar 125amp alternator and ARS-5 Balmar regulator, and after installing 3 Firefly carbon foam batteries I thought I had a bulletproof setup...but on startup I'll always show 15.4 volts on the battery monitor. And at the battery. And, more importantly, on the ARS-5 readout itself. The Cv voltage, the target bulk charge voltage, as read on the regulator, is the correct 14.4, as I programmed. So this is a deeper mystery than first thought. Many calls with Balmar tech support later, I'm led to believe the high voltage is due to a surface charge. It's true that if my house bank is down a ways, the regulator will bulk at 14.4...but for no reason it will flip back up to 15.4 at some point, and then back and forth randomly. The regulator just will not control it. Tech Support said one solution (that "another boat is doing successfully") is to put a switch in the brown ignition wire (it's in the harness) to "turn off" the alternator while things are acting up like this. No harm to the alternator. We don't want to fry our batteries...if you or anyone have more theories on this, I'm all ears.

Did the tech support elaborate on what he meant by surface charge?

The following assumes you had no other charging sources connected at the time you noticed the higher voltage outputs from the alternator.

How long does that 15V regulator output last?
You could briefly or intermittently get a higher unregulated output of the alternator if there were major changes in the load, such as a 12V reefer switching on or off.

Especially if you have already a full charge on the batteries and no other loads are connected. There is some delay built into the regulator response, to avoid oscillations, but within a few seconds at most, the output voltage of regulator should return to a proper value for whatever charging stage it was in, as long as the alternator can handle the load. In your case, a higher voltage means the alternator was easily able to supply enough current.


If the high output voltage persists more than a few seconds, it sounds like that regulator may have an actual problem, if you have confirmed that you have a good solid connection of voltage sense from battery to alternator.
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Old 09-07-2020, 17:52   #8
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Re: Voltage to spikes voltage

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Originally Posted by TrailerCruiser View Post
My alternator voltage puts out over 15 volts of power after it has been running for a while. The voltage starts out about right at around 13.6, But after the motor runs for a while it spikes up to over 15 volts. It stays there for a while then goes back to around 14 volts. Then is cycles back up to high voltage and back to normal voltage. The voltage fluctuates over time. What might be causing this issue? I've cleaned all the negative terminals as well has have cleaned off all the terminals. Any idea what might be causing this voltage fluctuations over time?
From what you indicate, I think all is ok... at rest with engine off you should read 12.8 volts at the batteries. Once started... the alternator output at the batteries should read anywhere from 13.6 to 14.7 volts with load on. Switch on accessories to see if the voltage drops... precision in measuring here is important before you start changing parts and to find out all was OK...
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Old 09-07-2020, 22:02   #9
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Re: Voltage to spikes voltage

If the voltage regulator has a voltage sensing connection to the battery terminal it is quiet possible that the alternator is putting out 15 volts in order to provide the 14.2-14.4 volts required to fully charge your batteries.
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Old 09-07-2020, 22:24   #10
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Re: Voltage to spikes voltage

Balmar tech support has treated me very well...lots of emails, and they switched out the regulator I'd installed last year in case it was defective not controlling these high voltages...but the new one was no different. Also was informed that no other of their regulators would likely solve the dilemma. Their idea of installing a switch was to be in the brown ignition wire...not the voltage sense (red, I believe) wire. I have not yet installed a switch, but when I see 15.4 volts, I feel very motivated to turn off the alternator somehow. It's not just when the house bank is full and trickling in a few amps...this happens randomly and sometimes in the 20+ amp range. That just cannot be good. I don't understand the concept of surface charge...but my Firefly batteries are still "new"...I wonder if their unique chemistry contributes to this somehow. The voltage does often pop down to the correct 14.4 or even float at 13. 4...so I feel there's hope...that there's some simple explanation. BTW LOVE the exchange of ideas on this forum...
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Old 10-07-2020, 00:13   #11
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Re: Voltage to spikes voltage

If you are concerned as to whether or not the excessive voltage is liable to damage your batteries you need to monitor the voltage across the battery terminals independent of the charging current conductors.
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Old 10-07-2020, 10:57   #12
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Re: Voltage to spikes voltage

Thanks for all the comments. When the engine panel reads in the red, greater than 15 volts, I tested the actual voltage at the battery terminals. They read 15.95 or greater using my voltmeter. Note it will stay in the 15+ range for a minute or so before kicking down to normal 13.8 volts or so. Then about two or three minutes later the voltage goes up over 15 again. This cycling never stops. The other day I ran at the dock for about 10 minutes while the charging never got over 14. Then eventually after 10 minutes the volts started to climb to around 16 volts.

Could a battery that is almost dead cause this kind of cycling? I have noticed one of my batteries appears to be too low to turn over the motor.
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Old 10-07-2020, 16:05   #13
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Re: Voltage to spikes voltage

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Originally Posted by TrailerCruiser View Post
Thanks for all the comments. When the engine panel reads in the red, greater than 15 volts, I tested the actual voltage at the battery terminals. They read 15.95 or greater using my voltmeter. Note it will stay in the 15+ range for a minute or so before kicking down to normal 13.8 volts or so. Then about two or three minutes later the voltage goes up over 15 again. This cycling never stops. The other day I ran at the dock for about 10 minutes while the charging never got over 14. Then eventually after 10 minutes the volts started to climb to around 16 volts.

Could a battery that is almost dead cause this kind of cycling? I have noticed one of my batteries appears to be too low to turn over the motor.
It is not a bad battery causing this but it sure will kill all your batteries if you continue.

Almost certainly the voltage regulator on the alternator. Replacement is quick and easy look for the oblong heat sink on the rear of the case usually held in by a screw at each end.

Modern stuff is pretty tolerant but 15+ volts can also do permanent damage to some 12v electronics.

The regulator may have failed due to bad bushes, a short, breaking the circuit, or a loose connection, while it is running. So check all the connections and the condition of the alternator especially if it dirty before fitting the new regulator.
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Old 10-07-2020, 16:23   #14
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Re: Voltage to spikes voltage

It sure sounds like you have a Balmar voltage regulator with the alternator temp sensor and the regulator is programmed to a high voltage, it can’t get to a high voltage initially because due to battery SOC, it’s current limited, but as they get charged the voltage can go high, but cuts back when the alternator temp climbs high enough, the regulator cuts back on alternator field current to keep from burning it up, it cools off and goes back to high voltage, gets hit and cycles.

I never noticed which regulator you have.

If it’s a Balmar, especially a 614, read this article and program your regulator exactly like he says, that will eliminate goofy programming as an issue
https://marinehowto.com/programming-...age-regulator/
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Old 11-07-2020, 09:04   #15
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Re: Voltage to spikes voltage

Quote:
Originally Posted by TrailerCruiser View Post
My alternator voltage puts out over 15 volts of power after it has been running for a while. The voltage starts out about right at around 13.6, But after the motor runs for a while it spikes up to over 15 volts. It stays there for a while then goes back to around 14 volts. Then is cycles back up to high voltage and back to normal voltage. The voltage fluctuates over time. What might be causing this issue? I've cleaned all the negative terminals as well has have cleaned off all the terminals. Any idea what might be causing this voltage fluctuations over time?
A64Pilot has given you very good advice. Suggest you also see if there is a load on the battery using a DC Amp meter... and watch that during cycle of voltage peak and so on. Sounds like there might be some kind of load. Load will produce heat somewhere... what is getting warm or HOT?

It may be that there is something that is triggering the voltage regulator to peak output. This can be done on some alternators via a rheostat to do rapid charging but at the expense of the life of the battery. It would also reduce the time the engine needs to be run to charge the battery. That is a custom installation done for racers usually. You probably do not have this modification if it is not labeled.

What is your boat and engine?

Look for high resistance or an isolation diode pack to separate batteries. This usually causes a 1 volt drop. These isolators can be tested. Look online.

Uncle B
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