Recovering Smart LiFePO4 with BlueSmart Charger, is my Cell Lost?

DIY
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Hy Community, i had bad winter days with mit Smart LiFePo4 Battery :confused:

I had my Smart LiFePO4 Batterie to long in my RV when it was around 0°C Outside. So charging was not possible.
Smart Shunt showed a SOC of ~15%, so that i was not in panik. But one day the Batterie did not came up in the Victron Connect App, so i opened the main batterie switch. Since conditions outside did not get better for 2-3 days, i took the battery inside my house and bought a Blue Smart Changer. (I read that it can charge theses batteries even from 0V). First Charging started at 10.52 battery voltage. Since i could not configure a Charge current below 5A in the Blue Smart Charger (wantet to charge with 0.1A first, as the manual recommends for undevoltage batteries), i hoped that 5A is also fine, since 10.52V did not looked SO bad.

I charged for some hours (with breaks over some days, since i needed to monitor it safely).
When i reached about 13V battery voltage and the bluetooth did not came back, i opened the battery to reboot the electronics, by disconnection it from + for some seconds. Bluetooth was back. I was able to monitor the Cells and they where surpisingly very equal (~3.29/3.3 V).

I added the sensors to home assistant, made an automation to toggle off the charger when cell drift is > 0.1V, cell voltage > 3.69V and battery tempetature > 45°C, then contiuned charging with 13.8V.

When i reached the Absorption Mode at ~13.8V, i changed the Charge voltage to 14.2V and the current to 10A.
My cell drift limit kicked in quickly, so i increased it to “> 0.2V”, then “> 0.3V”.
Then Cell 1 reached 3.66V and the Cell balancing started. Cell 2,3,4 balanced to about ~3.58V (+/- 0.01V), but cell 4 is now stuck at ~3.42(+/- 0.01V).

Now my Questions:
Is my Battery Lost?
Or can i continue without danger with one cell having a drift of 0.15V less then the others?
Is there anything i could try to also get this cell up? Give cell balancing more time?
How should i continue? Wait? Retry?
Did i made mistakes in the recovery process? (not starting with 0.01A but with 5A?)

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If anyone is interested in the home assitant sensor templates, i can share them here.(of course if possible use the victron BMS) but the blue charge has no remote on/off terminal, so i helped me with this and a smart plug infront of the charger.

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You have 2 cells that are standing out as different.

#1 could just be the lowest Ah cell in the pack and shot up in voltage as this result. This cells voltage settled down under charge / balancing. As per screenshot.

#4 could just be a little bit behind in Ah fullness, or it could now have damage that appears as higher self discharge, and will never reach / maintain the same voltage as the other cells.

If further monitored charging brings cell #4 up to the same voltage as the other cells monitor it very closely. Should its voltage drift lower than the other cells under use, it should be considered as broken. Battery is close to end-of-cycle life or has been misused

Your battery is damaged. This could result in lower capacity. Or this could result in the battery failing when it is needed.

1 Like
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Okay thank you for your fast response :slight_smile:

Then i will try to give the cell balancing some more time.

This are the full charging curves from today:
From 9:55 i increased charging voltage from 13.8 to 14.2V. Then the balancing started.

(The outtages are the result of my cell-drift limit kicking. Or when i stop manually.)

Zell 2 + 3 are also not so much equal.

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Is there any danger in further charging at this state? Or in using it with lower capacity?

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Cell 1 is now also climbing, and cell drift falling… how long should i leave it in cell balancing mode?

At this moment the charger does not push any more power into the battery… (~14.20V / 0.0A).

Should i stop after some minutes, and restart when cell voltage is rested for some minutes? Seems like that helped the last cell to come over the 3.42V.

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