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Old 03-09-2011, 13:00   #1
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voltmeter reading 13.25 down from just under 14 when motoring

I have a universal 25 MXP engine
The alternator is Westerbeke 12 Volt - 50 amps PN 41017

when I leave the docks, after an AC charge the voltmeter reads just under 14. After motoring awhile the voltmeter gauge at the binnacle drifts down to as low as 13.25. This is new. They used to stay up around 14 when I was motoring. I was not at anchor at all. just on the dock or motoring.

Is this most likely corrosion?
Old Batteries? (they are almost 5 years old)
Is the reading at the binnacle of the voltmeter at the binnacle gauge a combination of the batteries and the alternator or just one or the other?
When I get back to the dock the batteries are at 12. 91... and then go higher after an AC charge.
The engine is from 2010 as is the alternator.
The belt is tight.
The voltmeter at the DC panel in the boat reads just under 14. Does this indicate corrosion at the binnacle?

Should the batteries read higher after motoring?

Thanks for your thoughts,

Bonnie
Catalina 28
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Old 03-09-2011, 13:16   #2
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Re: voltmeter reading 13.25 down from just under 14 when motoring

Bonnie,
All you are measuring is what the charger regulators are doing, not what the batteries are doing. If you want to see the honest voltage of the batteries then fully charge them on the shore power, disconnect the charger and disconnect the batteries from any load. Let them settle for a few hours and then use a digital volt meter to read directly at the batteries. Depending on your battery type you should see something around 12.85v.
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Old 03-09-2011, 13:49   #3
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Re: voltmeter reading 13.25 down from just under 14 when motoring

Quote:
Originally Posted by cmyk.br View Post
when I leave the docks, after an AC charge the voltmeter reads just under 14. After motoring awhile the voltmeter gauge at the binnacle drifts down to as low as 13.25. This is new. They used to stay up around 14 when I was motoring. I was not at anchor at all. just on the dock or motoring.
[...]
Should the batteries read higher after motoring?
To me it looks like alternator stopped charging for some reason. If you leave dock with a fully charged battery and have no excessive power consumption the voltage should get back to above 14V not long after engine is started.

When you continue motoring for longer, or add more power consumption, will the voltage drop below 13.25V or will it stay there?
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Old 03-09-2011, 14:16   #4
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Re: voltmeter reading 13.25 down from just under 14 when motoring

just means you have been charging batteries and are fuller of electricity than they were when you started. brand new batteries are not necessarily fully charged. mine were not. had same thing happen. fully charged batteries not on a charger should read 12.71. while charging, should read anywhere from 13.6-14.something. mine were reading 15.6 as they charged. was weird seeing such high numbers.
if you wish to check my knowledge, there are battery maintenance sites online. look it up. you should be charging at a 13+ number for most of your charging time.
depending on your alternator on your engine, charging time can be anywhere from one week, with a 35 amp alternator on a 8d battery, to a few hours with a 35 amp alternator on golf cart batts. an 80 amp alternator takes a little less time but not truly too much as the type of battery indicates the charging of them---some need slow charging, some can be charged fast. if you have golf cart batts, they are charged slow. a lead acid 8d can be fast charged.
i really think your system is fine. is doing exactly wjhat is spozed to be doing---slowing down charge as the batteries become more fully charged.
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Old 03-09-2011, 14:34   #5
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Re: voltmeter reading 13.25 down from just under 14 when motoring

Quote:
Originally Posted by cmyk.br View Post
I have a universal 25 MXP engine
The alternator is Westerbeke 12 Volt - 50 amps PN 41017

when I leave the docks, after an AC charge the voltmeter reads just under 14. After motoring awhile the voltmeter gauge at the binnacle drifts down to as low as 13.25. This is new. They used to stay up around 14 when I was motoring. I was not at anchor at all. just on the dock or motoring.

Is this most likely corrosion?
Old Batteries? (they are almost 5 years old)
Is the reading at the binnacle of the voltmeter at the binnacle gauge a combination of the batteries and the alternator or just one or the other?
When I get back to the dock the batteries are at 12. 91... and then go higher after an AC charge.
The engine is from 2010 as is the alternator.
The belt is tight.
The voltmeter at the DC panel in the boat reads just under 14. Does this indicate corrosion at the binnacle?

Should the batteries read higher after motoring?

Thanks for your thoughts,

Bonnie
Catalina 28
I am assuming then that all the reading you give are being taken from the binnacle meter.

1. the volts should read the same on both meters all the time. If they don't then at least one of the meters is faulty.

2. It is pointless trying to work out if there is something wrong if the test equipment (ie your voltmeter) is giving incorrect readings.

3. Check and record the meter readings as various stages on both meters and if different get a third hand held meter and read direct from the battery. Hopefully it will agree with one of your fixed meters and so point out with one is then faulty.

4. Until you are sure that at least one meter is correct, you can't make an accurate assessment of your system.

5. My bet is that the binnacle meter has corrosion either in the leads / connectors or in the meter itself.
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