Help needed for a catamaran with acute elecronics problems

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truwas asked May 7, '24

Help needed for a catamaran with acute elecronics problems

Hi,
I am reaching out to you or you community for a catamaran sailing on the pacific. The crew reports a problem with their batteries. This is what the captain wrote to me (they can communicate with me by InReach):

"We have lifepo4 batteries 12v 1000Ah, 20 cells with 8xbms, 2x victron mppt solars, victron cerbo and smartshunt, victron multiplus 3000, bcu ppak+4c battery control unit. All has worked fine since 2021. Now the batteries are not taking charge. They quickly get to max voltage (14.2), and discharge quickly at night, so the boat goes dark. I can restore power by resetting the battery controller and running the engine or generator. I first saw the problem 3 days ago and it is quickly getting worse. No errors reported by system, all 8 bms lights are green. Connections look good and nothing is getting hot. I tried setting different soc % levels manually and it makes no difference. We need to know what it may be and what can we do to keep the lights on."

I would be grateful for any help.

Thank you!

battery

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2 |3000

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klim8skeptic ♦ commented · May 08 at 12:02 AM

@truwas I assume you have read the BCU manual, and the CBM manuals?

Have you followed the commissioning procedure in the BCU manual to test the continuity of the signal wire chain through the CBM's to the BCU? Does the latching relay/contactor open? Does the relay/contactor close when the BCU is reset?

Sounds like a stuck relay/contactor??

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Answer 1 · 2024-05-08T15:15:25Z

madmaxx answered · May 08 at 03:15 PM

A sentence like "We have lifepo4 batteries 12v 1000Ah, 20 cells with 8xbms, 2x victron mppt solars, victron cerbo and smartshunt," is not a replacement for a wiring diagramm.
"They quickly get to max voltage (14.2)," is not a quantitative description. If the batteries needed much more time for charging in the past, you need to quantify that and post current figure - a bug report always contains how you expect something to work and how it is currently working (which is the unexpected way).

Therefore I can only give you some generic advice. You have a supply/demand imbalance.

During daytime charge all batteries to the target voltage and disconnect all electrical loads. Measure consumption now - there might be a parasitic current drain. Then switch each electrical circuit on and note the current consumption. Compare the current consumption to the expected one - are the differences (overconsumption)?

If you can exclude that type of error you have to check to supply side, the batteries.

What is the voltage when you are "in the dark"?
What is the charge current?

Does the charging terminates much earlier than the charge current compared to the battery capacity suggests?
In this case you might have a cell imbalance within one or more 12V batteries.
Such a case would require opening the 12V batteries but I won't go into the details.

The inability of your crew to do simple diagnosis unfortunately suggests to ask for help in the next harbour.

2 |3000

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