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Old 03-12-2019, 11:46   #1
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Ground Leak / Voltage Drop? Beny OC41 2015

Hi,
I'm assisting a friend that is at sea on his Oceanis 41 2015 and has an electrical problem:

It seems that batteries are discharging faster than usually with a given load.

AGM Batteries has been individually isolated and keep there voltage. So We assume battery are in good condition. (They were replaced 8 months ago)

At the boat Monitor, Voltage shows max 12.5, while portable voltmeter read more than 13.5 direct in batteries while charging.

When solar panel or alternator recharge ends, the voltage drop around 12.3-12.5Volts.

Could it be a known problem that some of you had on a Beneteau Oceanis of 2015 era?

Any help would be greatly appreciated.

Thanks!
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Old 03-12-2019, 12:19   #2
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

First question would be regardless of type boat is anything on.

Are any of the normal loads for the batteries turned on?

If not, have you checked/redone the connections at the battery and elsewhere?

When you measured the voltage at the battery did you put the leads on the battery posts or the terminals/connectors?
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Old 03-12-2019, 12:27   #3
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

Quote:
Originally Posted by SV Rosy View Post
Hi,
I'm assisting a friend that is at sea on his Oceanis 41 2015 and has an electrical problem:

It seems that batteries are discharging faster than usually with a given load.

AGM Batteries has been individually isolated and keep there voltage. So We assume battery are in good condition. (They were replaced 8 months ago)

At the boat Monitor, Voltage shows max 12.5, while portable voltmeter read more than 13.5 direct in batteries while charging.

When solar panel or alternator recharge ends, the voltage drop around 12.3-12.5Volts.

Could it be a known problem that some of you had on a Beneteau Oceanis of 2015 era?

Any help would be greatly appreciated.

Thanks!
There is no benefit from looking at model-specific issues.
Start by chasing the difference between 12.5V at battery monitor and 13.5V at battery terminals. If you want to get this right then take no shortcuts.

Draw a schematic showing every piece that connects the positive terminal of the house battery to the positive terminal of the battery monitor.

Then do the same on the negative side.

Then, starting with battery at lowish state of charge, run engine and measure voltage drop between negative terminal of house battery and negative terminal of battery monitor. Then measure drop in each piece in between negative terminal of house battery and negative terminal of battery monitor. The sum of all the component drops on negative sideshould add up to the total drop on negaitive side. Do the same on positive side.

Now identify the largest component drop. At one of the ends of that piece there is a bad connection, which will be be hot to the touch (and show itself with an infrared camera). Clean and tighten that connection and repeat.

Usual suspects are: a) ground point at engine b) combiner relays or diodes.

Good luck
Repeat
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Old 03-12-2019, 14:39   #4
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

Thanks for the replies.
Svlamoracha, thanks for the specific detailed procedure. I'll pass him on the message on how to check for the drops.
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Old 03-12-2019, 16:35   #5
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

What voltage is he charging the batteries to? He may have been undercharging the batteries which could mean an early death for AGM. Depending on the make of the AGM he may be able to do an equalization charge but that would be pretty much impossible while at sea.

Charging voltage should be around 14.4 volts depending on manufacturer specifications. For instance "Lifeline recommend a Bulk and Absorption voltage of 14.3 Volts at standard temperature. For a float voltage they recommend 13.3 Volts at standard temperature. "

He should also be charging so that the batteries reach a full charge. His alternator charging should be done before/at dawn so that the solar charger can top up the batteries during the day.
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Old 03-12-2019, 18:52   #6
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

DeepFRZ, that's what triggered is concerns. The fact the solar panel could not charge the batteries at normal charging voltage, around 14,4 volts, and obviously the system could not get in absorbions or floating mode.
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Old Yesterday, 07:43   #7
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

When my system will not charge all the way up then go to float mode, the first thing I do is grab all the wires on the controller and move them. (or try to move (reseat) them individually)

90% of the time that fixes the problem. Sometimes though it's a battery cable. An old or bad battery can do the same

How is it with all loads off?


Ps. I only have solar so if you have two charging sources and both are doing the same thing it's probably not the controllers but could still be connections
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Old Yesterday, 09:19   #8
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

As previously mentioned by others, the exact voltages are fairly critical. It hasn't been mentioned but, are the voltmeters digital voltmeters? Check the voltmeter against a known DC standard voltage.
There is an old Chinese saying: "A man who owns a watch knows what time it is; a man who owns two watches is never sure".
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Old Yesterday, 09:33   #9
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

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As previously mentioned by others, the exact voltages are fairly critical. It hasn't been mentioned but, are the voltmeters digital voltmeters? Check the voltmeter against a known DC standard voltage.
There is an old Chinese saying: "A man who owns a watch knows what time it is; a man who owns two watches is never sure".
The assumption is that the battery monitor used to read the higher voltages all the way up to the 14.4 volts he mentioned.

The 2nd assumption is that it did this for a relatively long period time (months - years) with the resulting worry of a problem when it began to show lesser voltages and immediate drops in voltage after charging

It's about as good as it gets with online troubleshooting when given bits and pieces of data
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Old Yesterday, 12:21   #10
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

If solar cannot charge, not only check connections of course, but also check inside the connection boxes mounted on the back of the panels (if you have them). I have found the + wire completely dissolved away inside boxes as they came from the factory after 4-5 yrs. Reseal with 3 individual layers of liquid tape/Marine Goop etc. Moisture is insidious!
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Old Yesterday, 14:54   #11
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Re: Ground Leak / Voltage Drop? Beny OC41 2015

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If solar cannot charge, not only check connections of course, but also check inside the connection boxes mounted on the back of the panels (if you have them). I have found the + wire completely dissolved away inside boxes as they came from the factory after 4-5 yrs. Reseal with 3 individual layers of liquid tape/Marine Goop etc. Moisture is insidious!
He said both charging systems had the same results so branching off and chasing one is a waste of time
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