House SOC while on shore power

D

Decisions

.
Nov 23, 2025
3
Beneteau Oceanis 41 San Diego
Hi all,

Newbie here but I am out of ideas and hope you can help. I have a 2024 Oceanis 40.1. While on shore power the House SOC continuously drains 1% to 2% a day. I thought this might be a battery preservation program but apparently not. I have seen it drain all the way to 30%. If I start the engine it charges right up and then drains right back down. I have asked our maintenance team and they have asked Beneteau but just crickets. I think there is a miswiring in the converter or perhaps a short somewhere. We have lost a couple of house breakers that have been replaced under warranty but I think something else is going on.

any ideas?

Thanks all!

Dan
 

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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,727
CAL 35 Cruiser #21 moored EVERETT WA
Welcome Dan to the SBO forum and your new boat.
  1. What type of batteries do you have for your house?
  2. While on Shore Power, do you have the charger turned on?
  3. Do you have a bilge pump? Is to pumping water out of the boat?
 
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D

Decisions

.
Nov 23, 2025
3
Beneteau Oceanis 41 San Diego
Hi!

I have epsilon super b lithium batteries.

I thought the battery charger was automatic on shore power? Will research.
edit: I am not at the boat but your question made me wonder if the batteries ever get charged off shore power. I honestly don’t know and it may be because the source is set wrong on the boat. <head smack> will check next week.

Yes on the bilge pump but the bilge is bone dry and I don’t think that is the issue.
 
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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,727
CAL 35 Cruiser #21 moored EVERETT WA
Lithium batteries can have a 1% parasitic discharge. You will need to check with the specific battery manufacturer. This usually is not a problem with large battery banks. It is dealt with by regular charging. If your charging system is not on while attached to shore power, you may resolve the issue by correcting that problem.
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,408
Hunter 310 West Vancouver, B.C.
@Decisions , by your chart it looks as if there is a periodic discharge of ~1% SOC which occurs every ~1.2 days in a very short period of time, maybe one minute or less. Assuming that the representation of the chart is proportional to the electrical discharge.

1764044969074.png


Don't know the size of your battery bank so can't say how many amps this represents but it's fairly large. Of course your batteries are not being charged at this time.

I can only suggest you invest some time in looking for this source of heavy discharge. Sorry, but I can't imagine what the load might be. Bilge pump maybe ?

Hook up the charger to your batteries and see if this phenomenon disappears. If it doesn't, write back. Doesn't tell you WHAT is pulling the amps but puts you back to the correct operation.
 
D

Decisions

.
Nov 23, 2025
3
Beneteau Oceanis 41 San Diego
That’s 1% per day more or less, and I am not sure why the drop off. It almost feels scripted. The date scale is at the bottom, and you will note that it is from 16 Nov - 23 Nov. I appreciate the direction. Ultimately there isn’t anything terribly mysterious about this. Battery’s are draining and the shore power isn’t charging. A volt meter should tell me what’s up. I will let you all know what I find out. Won’t be back on the boat until about 10 Dec.

Thank you!
 
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