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Old 02-03-2015, 01:05   #1
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12 Volt System Shows 15 Volts

Back again, with another dumb question, but gotta ask it.

On my recently purchased boat with the PO 9,000 miles away, I have "inherited" a Shenglong (Chinese make) solar array with five, 85 watt panels. The storage for the system is two, 12 volt "house batteries" in parallel configuration. A power distribution system can link them to the diesel battery, if extra power is needed to the start the engine.

The engine battery and house batteries are apparently hooked up to an instrument panel that has a gauge for the house batteries, and one for the engine batteries. Both, read approximately 15 volts.

The gauge which I believe is connected to he house batteries fluctuates between 13.5 volts and 15 volts, and I can hear a clicking noise from the distributor each time the power fluctuates up to 15V. The gauge which I believe is connected to the one engine battery does not fluctuate, but stays at about 15 volts.

I am wondering why this is so, because I was told that the system is a 12 volt system, and I have run 12 volt LED lights off it with no problem.

Can anyone clarify this for me? Nothing I have read so far seems to address this apparent anomaly.

Thanks to all,

G2L
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Old 02-03-2015, 01:28   #2
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Re: 12 Volt System Shows 15 Volts

What is the controller? And what is the gauge?

Sorry to be cryptic but you could be reading panel voltage not regulated voltage. We could do 20 questions but better to take picture of your controller and your gauge and post them.
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Old 02-03-2015, 01:30   #3
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by Ex-Calif View Post
What is the controller? And what is the gauge?

Sorry to be cryptic but you could be reading panel voltage not regulated voltage. We could do 20 questions but better to take picture of your controller and your gauge and post them.
Yeah, I figured somebody would say that. Will go the photo route; but give me about 24 hours.

Thanks,

G2K
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Old 02-03-2015, 01:37   #4
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Re: 12 Volt System Shows 15 Volts

Yup - You could be making 35 amps and at 15 volts that could be a battery killer.

Presuming you have ~250 a/h capacity?
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Old 02-03-2015, 02:00   #5
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Re: 12 Volt System Shows 15 Volts

Charging a battery requires a voltage higher than the rated battery voltage. Automotive type battery voltage during charging is 14.3 to 14.8 but can go as high as 15.1. A fully charged battery (not being charged) should read 12.6 with each cell producing 2.1 volts.
Most DC equipment can tolerate a wide variance in voltage.
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Old 02-03-2015, 03:47   #6
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Re: 12 Volt System Shows 15 Volts

Panel meters are not accurate, think less so when they get older. Voltage is easy to check, You should have a AVO (Multimeter) some are more accurate than others, I would also recommend a DC clamp meter, suitable for convenient but not necessarily accurate measuring DC amps.
Check on line for maximum rated voltage for your batteries, then compare that value, with the voltage across battery terminals when on charge.
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Old 02-03-2015, 10:45   #7
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Re: 12 Volt System Shows 15 Volts

12Vdc is the nominal voltage. When fully charged, the no-load voltage will be 12.8Vdc. When 50% discharged, it will be 12.2Vdc. During the charging process it could be as high as 14.2 Vdc.


Note: The instant you find a leak in your hull, start the bilge pump, and then the engine. The electric bilge pump will output much more with 14.2 Vdc connected then 12.2 vdc.


Back to the subject at hand.


First, you should not need to combine your house bank to your starter battery to start the engine (under normal circumstances). The only rare occasion, would be if your starter battery was dead, (ie, significant fault, battery, alternator, or wiring).


Your house bank, when fully charged, will be at 12.8 Vdc. Your alternator or solar charge controller should deliver no more than 14.2 Vdc when operating properly, under a normal charge cycle.


15Vdc is higher than you should be seeing from a regulated charge controller. (This could be just inaccuracy of your analog panel meter.)


By the term "distributor" it sounds like you are referring to an ACR (automatic charging relay). The purpose of the ACR is to combine the house and starting batteries to the charging system(s), only when operating, so all batteries are charged. Conversely, the purpose is also to disconnect house and starting batteries when not being charged, so that house loads will not discharge the starter battery.


If wired correctly, when the solar charge controller or alternator output voltage reaches the ACR activation threshold voltage, it "clicks" on, and combines the house bank to the engine battery. When the drops below the ACR threshold, it "clicks" off and disconnects the starter battery from the house bank. (There is some span between the on and off thresholds to avoid chatter.)


Unless you are very well versed in electrical systems standards and practices, don't meddle; hire a CERTIFIED Marine Electrical or Electronic Technician. Batteries contain enough energy to quickly burn your boat to the waterline if wired incorrectly. Way too many people with way too little knowledge inadvertently make changes that will not pass a survey, and put their boat and precious cargo at risk.


Rod Brandon
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Old 02-03-2015, 10:56   #8
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Re: 12 Volt System Shows 15 Volts

Most voltmeters should be treated as "indicator only" unless you've checked the calibration.

I bought two $20 digital meters from Amazon, but checked them against a calibrated Fluke at work. At 12V they were both within 50mV. Good enough.

I bought a 2" panel analog voltmeter for the engine panel that reads a remarkable 1V low! The quality analog voltmeter down below, reads about .2V low.
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Old 03-03-2015, 04:42   #9
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Details of System- Re: 12 Volt System Shows 15 Volts

Quote:
Originally Posted by Ex-Calif View Post
Yup - You could be making 35 amps and at 15 volts that could be a battery killer.

Presuming you have ~250 a/h capacity?
Not sure what you mean by a "battery killer", but the batteries seem to be working fine.

Tried to post some photos, but could not get the wife's smart phone to cooperate. In any case, the details I can give are the following:

The 5, 85 watt solar panels are from the Shenlong company and are rigged in parallel structure. So are the two Motolite, 12 volt batteries.

The power distribution "panel" is made by Blue Sea Systems and it has "12v DC DISTIBUTION" listed at the top of the panel. It also shows a "Max 32 V DC/300A CONT./450 A INT. rating on it the red knob used to switch settings. The circular red knob allows you to move it one half turn to the right, from "off" to "on". It has a Dual Circuit" notification between the on and off settings and three yellow lights above the knob and below two 15 volt fuses and apparently a 100 amp circuit breaker. Moving the knob a 1/3 turn right, moves it into a yellow caution area that reads "combine batteries".

The volt "gauges" are on a separate, owner built panel and, as noted previously, the house gauge moves from 13.5 to 15 volts, apparently when charging in sunlight, and the other gauge stays at 15v. There are also two amp gauges, but, unfortunately, neither works. There are no company names on these 4 gauges or on the panel, which also has various switches for turning on and off various circuits.

So, that is what the array and two panels "look like".

Hope to get some pictures up soon.

Anybody who has an idea what is going



a
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Old 03-03-2015, 04:43   #10
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by Lepke View Post
Charging a battery requires a voltage higher than the rated battery voltage. Automotive type battery voltage during charging is 14.3 to 14.8 but can go as high as 15.1. A fully charged battery (not being charged) should read 12.6 with each cell producing 2.1 volts.
Most DC equipment can tolerate a wide variance in voltage.
got it. thanks. that helps.

g2l
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Old 03-03-2015, 04:44   #11
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by Oceanride007 View Post
Panel meters are not accurate, think less so when they get older. Voltage is easy to check, You should have a AVO (Multimeter) some are more accurate than others, I would also recommend a DC clamp meter, suitable for convenient but not necessarily accurate measuring DC amps.
Check on line for maximum rated voltage for your batteries, then compare that value, with the voltage across battery terminals when on charge.
OK, will do. thanks

g2l
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Old 03-03-2015, 04:53   #12
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by ramblinrod View Post
12Vdc is the nominal voltage. When fully charged, the no-load voltage will be 12.8Vdc. When 50% discharged, it will be 12.2Vdc. During the charging process it could be as high as 14.2 Vdc.


Note: The instant you find a leak in your hull, start the bilge pump, and then the engine. The electric bilge pump will output much more with 14.2 Vdc connected then 12.2 vdc.


Back to the subject at hand.


First, you should not need to combine your house bank to your starter battery to start the engine (under normal circumstances). The only rare occasion, would be if your starter battery was dead, (ie, significant fault, battery, alternator, or wiring).


Your house bank, when fully charged, will be at 12.8 Vdc. Your alternator or solar charge controller should deliver no more than 14.2 Vdc when operating properly, under a normal charge cycle.


15Vdc is higher than you should be seeing from a regulated charge controller. (This could be just inaccuracy of your analog panel meter.)


By the term "distributor" it sounds like you are referring to an ACR (automatic charging relay). The purpose of the ACR is to combine the house and starting batteries to the charging system(s), only when operating, so all batteries are charged. Conversely, the purpose is also to disconnect house and starting batteries when not being charged, so that house loads will not discharge the starter battery.


If wired correctly, when the solar charge controller or alternator output voltage reaches the ACR activation threshold voltage, it "clicks" on, and combines the house bank to the engine battery. When the drops below the ACR threshold, it "clicks" off and disconnects the starter battery from the house bank. (There is some span between the on and off thresholds to avoid chatter.)


Unless you are very well versed in electrical systems standards and practices, don't meddle; hire a CERTIFIED Marine Electrical or Electronic Technician. Batteries contain enough energy to quickly burn your boat to the waterline if wired incorrectly. Way too many people with way too little knowledge inadvertently make changes that will not pass a survey, and put their boat and precious cargo at risk.


Rod Brandon
www.SheenMarine.com
Rod,

Thanks a lot for the thorough explanation. Mixed w. the other comments above, I have a MUCH better handle on what is going on. I absolutely do not want to mess with the system myself, especially if it apparently is working as it should.

Will do the research and multi meter checks suggested by folks on the thread, and hopefully the system will turn out to be working as it should. There is no physical evidence to suggest a problem at this point, but I intend to buy a 40 watt, 12v fan, and I want to make sure all is in order before wiring it in.

Thanks again,

G2L
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Old 03-03-2015, 04:55   #13
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by MarkSF View Post
Most voltmeters should be treated as "indicator only" unless you've checked the calibration.

I bought two $20 digital meters from Amazon, but checked them against a calibrated Fluke at work. At 12V they were both within 50mV. Good enough.

I bought a 2" panel analog voltmeter for the engine panel that reads a remarkable 1V low! The quality analog voltmeter down below, reads about .2V low.
Yeah, I doubt that the meters are extremely accurate. More like educated guesses, I would think : )

Thanks,

G2L
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Old 03-03-2015, 06:01   #14
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by Gone2long View Post
There is no physical evidence to suggest a problem at this point, but I intend to buy a 40 watt, 12v fan, and I want to make sure all is in order before wiring it in.

Thanks again,

G2L
Unless you consider that you stated your battery voltage was 15V....

I don't see any solar controller listed in your description, all I see is PV to a Blue Sea panel. Blue Sea does not make solar controllers.... If you don't have a solar controller you will eventually ruin the batteries.

Upper end charge voltage for most deep cycle flooded lead acid batteries is 14.7V at 25C / 77F. The 14.1V to 14.7V adsorption stage of charging is not a permanent safe charging voltage and it should drop to a float voltage well under 14.0V once the batteries are at about 98% SOC or close to it. Most important is to find your battery specifications for absorption and float voltages. Each battery will be slightly different but most often between 14.1V & 14.7V for absorption and 13.0V and 13.8V for float.

Measure the voltage at the battery terminals with something more accurate than the panel voltmeter. If you see 15V then you need to track down your controller and adjust it for your batteries. If there is no solar controller you should invest in one...
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Old 03-03-2015, 06:09   #15
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Re: 12 Volt System Shows 15 Volts

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Originally Posted by Gone2long View Post
Not sure what you mean by a "battery killer", but the batteries seem to be working fine.
Too high a voltage for the charging regime of your battery type can "boil" the batteries. All things equal higher voltage will result in higher temps and the battery (even sealed ones) will eventually gas off.

Thanks for the great description of your system.

Quote:
Originally Posted by Maine Sail View Post
Unless you consider that you stated your battery voltage was 15V....

I don't see any solar controller listed in your description, all I see is PV to a Blue Sea panel. Blue Sea does not make solar controllers.... If you don't have a solar controller you will eventually ruin the batteries.

<snip>
Measure the voltage at the battery terminals with something more accurate than the panel voltmeter. If you see 15V then you need to track down your controller and adjust it for your batteries. If there is no solar controller you should invest in one...
What he said. Find the solar controller and let us know what it is. With the system gauge measuring 15+ volts measure across the batteries and compare.

This could be as simple as a badly calibrated panel gauge.
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