Multiplus Lifepo4 cycling (switching 230v off also) on and off at 100% SOC

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johnathan-briggs asked Dec 22, '20

Multiplus Lifepo4 cycling (switching 230v off also) on and off at 100% SOC

hi

I have a 10 year old, 12v multiplus with inverter. I have just swapped my LA batteries for 2x 12v 200Ah LifePO4 batteries in parallel, each with a 100AMP BMS.

Using the V2 cable I have reconfigured the multiplus with the following settings.
https://photos.app.goo.gl/c2NyS5tVva36wdkXA

With the battery isolator switched on and a slight load all seems to work perfectly. However when I open the battery isolator switch (ie turn off the boat's house power ) the multiplus cycles on and off and at the same time switches on and off the 230v supply. The batteries are at or close to 100% SOC.

I switched the config to the Victron default LIfepo4 config and the issue is the same.
Here is a short video showing the cycling on and off of the multiplus. Note charging is cycling but also the 230volt mains supply is switched on and off.

https://photos.app.goo.gl/uHMQDZyMHLNhB5RHA

I'm not sure if this is helpful but this is the log of the BMS https://photos.app.goo.gl/qRuohrKCm6ZgGURXA

Please can anyone offer me some advice.

Thank you

Johnathan

MultiPlus Quattro Inverter Charger Lithium Battery

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2 |3000

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johnathan-briggs commented · Dec 23, 2020 at 08:29 AM

Thank you for your replies, I really appreciate it. We are only 3 days from a full lockdown here and the boat yard is closing for 1 month. I'm desperate to get the 230V supply working again (when the batteries are off) so I can at least run the dehumidifier.

The BMSs (2x) I am using are 4s BMS 120a LifePo4 Battery Management System for 12v DIY Batteries, Programmable, Bluetooth Included. – Overkill Solar
Each is connected to 4x LFP cells to make two batteries. The two batteries, each with the own independent BMS are connected in parallel as a single battery bank.
My multiplus is using firmware that I think will date back to 2007 - Will this be a problem?
I do not have a two wire BMS configured, looking at the BMS there is a 'allow discharge' switch but I don't see a disconnect charger switch.

The shore power runs directly to the multiplus, so when it shuts down so does my all my 230V boat circuit which runs my dehumidifier and some heating. The two charging circuits are directly connected to a LA starter battery and the new LFP battery bank. Each of these banks has an output to the engine / house supply with separate isolator switches.

I'm unclear how this should work in theory or what the multiplus is shutting down.

Will the multiplus shut down if it senses 0v across the battery (BMS output) - is this the likely reason for the shutdown? If so I assume that this is likely happening because the BMS detects a problem state and opens the circuit to protect the cells. At near or 100%SOC what should the BMS do? Does it disconnect the charger or does the charger itself sence the SOC and stop the charging? If so, in my case is the likely case that the BMS is stopping the charger before the charger can sense the voltage to stop?

Also, I made up the batteries at home in September. They have been sat since then, with one small charge. I did notice the cells did not seem as well balanced when I connected them up in the boat this week.

I would be grateful for any advice, direction or links for me to research.

Thank you for your help - I really appreciate it.

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Answer 1 · 2020-12-22T21:54:34Z

bathnm answered · Dec 22, 2020 at 09:54 PM

It looks like your BMS is triggering cell over voltage, which means the BMS will disconnect charge and the charger will switch off. With some load the cell voltage will not rise and therefore not trigger. Do you have the two wire BMS configured on the MultiPlus? What is triggering the Multiplus to stop charging?

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Answer 2 · 2020-12-22T22:15:59Z

Daniël Boekel (Victron Energy Staff) answered · Dec 22, 2020 at 10:15 PM

Not knowing what kind of BMS, how it is connected to the inverter, etc. the only thing I can say is '14.6 volt is very high for an LFP battery'

try 14 volts first, or even lower if the battery is not yet balanced.

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