Multiplus II GX Battery monitor SOC drifts

Hi Community,

the Battery monitor of my Multiplus II GX shows wrong low SOC % from time to time. In the chart below you can see a long decay from 13. July to 20. July.

During this week there was no correct SOC %. The battery voltage was charged to full 57.6 V every day but for any reason the Battery monitor did not get this correctly and SOC declined from day to day.

I noticed that during those days the charger does not run in bulk or absorption mode, it remains in Float mode all the time.

The only way to reset the SOC back to 100% was to reduce ESS minimum SOC down to 50%. When it gets that low, the next day it charges in bulk and absorption mode again and jumps from 50% to 90% SOC in one hour !

What is wrong here and which setting could improve this behaviour ?

Thanks for your help.

Daniel

2 |3000

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Alexandra ♦ commented · Aug 09, 2020 at 01:06 PM

@daniel1976

Are these managed lithium batteries or lead based?

Is battery life set in the ess menu?

If not then the system may not be getting to 100% every day. Using voltage is not a very accurate way to determine charge at all, rather using something like a coloumb counter is better like a BMV. A BMV 'counts' the energy that has moved in and out of the battery, this is important when you understand how the Victron works out SOC.

What state the batteries are in the charge cycle is determined by the amperage going into the batteries at the time, so if you have good solar you will move through the cycle to where there is no draw - float. The problem is if solar was not good enough then float will be the seen state as the current going in is not high even if the battery is not fully charged.

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