Cell balancing 48v battery bank, 2 out of 6 batteries status unknown

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cronblad asked Dec 5, '23

Cell balancing 48v battery bank, 2 out of 6 batteries status unknown

Hello,

I charged the 200ah 24v individually before connecting them in series and as you can see in below picture two batteries balance well but does not change status from unknown to balanced as the other four does. In the standard ess settings absorption time is 1hr but I have read that 2hrs is recommended. I can change it, no problem to hopefully give time for proper balancing but..

1. Why is the standard ess setting 1hr while recommendation is 2hrs?

2. Why does the four out of six batteries reach status balanced given the same starting conditions?

/Daniel

Battery Balancer ess settings

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Answer 1 · 2023-12-05T22:36:14Z

klim8skeptic answered · Dec 05, 2023 at 10:36 PM

@Cronblad If you click on the "info" button Victron Connect will give an explanation of what "Unknown" means, and what is required to remedy the situation.

As per the Smart Lithium Battery manual. The cell balancing process is nearing completion when all cells have reached a voltage of 3.55V and the charge current has dropped below 1.5A. Balancing is complete when the charge current has dropped even further.

vc-batt-status.png (325.7 KiB)

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cronblad commented · Dec 06, 2023 at 08:01 AM

Thank you! According to definition of "Unknown" any cell imbalance shall be detected when battery is above 13,8v x 4= 55,2v. My max charge voltage is set to 56,8v per the manual so this one should be ok.

Regarding the note:

First prerequisite: "The cell balancing process is nearing completion when all cells have reached a voltage of 3.55V and the charge current has dropped below 1.5A. Balancing is complete when the charge current has dropped even further" 3,55v per cell = 3,55v x 16 cells in my case (48v system)= 56,8v This prerequisite is fulfilled.

Second prerequisite: The only thing I can think of right now that keep the batteries from reaching "balanced" status is that 1hr absorption time is not enough for the charge current to drop below 1,5A. Hope someone can explain my question no.1 above why 1hr is set as standard in the ESS if it´s not enough.

And also, why has 4 out of 6 batteries reached status "balanced" and not the last 2?

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Answer 2 · 2023-12-06T10:32:31Z

klim8skeptic answered · Dec 06, 2023 at 10:32 AM

@Cronblad And also, why has 4 out of 6 batteries reached status "balanced" and not the last 2?

As per the manual, "unknown" means the battery has not been fully charged and fully balanced in the last 30 days.

Solution? Charge the batteries as per manual until their status goes to "balanced".

To keep the batteries happy and balanced you need to ensure that they spend enough time in "absorption" every month, as outlined in the manual.

As per why ESS only has 1 hour absorp time, dunno. Perhaps they expect the batteries to be fully charged every couple of days??

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cronblad commented · Dec 06, 2023 at 12:15 PM

Thank you! Appreciate it!

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Answer 3 · 2024-01-01T17:11:59Z

cronblad answered · Jan 01 at 05:11 PM

Edit: Problem eventually sorted by disconnecting the batteries that did not balance and charged them stand alone over and over a few times.

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