Victron 200Ah LiFePO4 - cell balancing

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mnentwig asked Dec 9, '18

Victron 200Ah LiFePO4 - cell balancing

Hello,

I have 2 Victron 200Ah LiFePO4 Smart connected in series to a 24V System. After a couple of charging cycles to 100% SoC with my Multiplus 24/3000/70 I see via Victron Connect App that the 1st Bat (connected to Minus of Multiplus) has a perfect cell balancing. It has 3,37 / 3,36 / 3,36 / 3,37V so 1 mV max difference. The 2nd Bat which is connected to plus of the 1st Bat and Plus of the Multiplus is not well balanced. It shows 3,38 / 3,34 / 3,36 / 3,38 so 4 mv difference. I applied the method described in the Bat owners manual: charging w/ const current < 2,0A until Bat reaches 14,2 V. 14,2 V were reached after 1.5 hours. Balancing state at the end of this procedure was 3,53 / 3,55 / 3,59 / 3,59V so 6mv hence no success. Any idea what I have to do can do? Thanks for any hints.

Michael

Lithium Battery BMS

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Answer 1 · 2018-12-11T19:11:45Z

Johannes Boonstra (Victron Energy Staff) answered · Dec 11, 2018 at 07:11 PM

Please repeat the individual stand alone charging of the batteries with a 12V charger (2h Absorbtion at 14,2Vdc) and prevent a deep discharge (as thats contributing to unbalance)

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Answer 2 · 2018-12-15T06:34:34Z

mnentwig answered · Dec 15, 2018 at 06:34 AM

Thanks, Johannes. Just started it a minute ago. I bought the batteries, put them together to a 24V bank in a test setup at home to charge them right after purchase and from then onwards on a monthly basis to bridge time until they will go into my truck which is now. So so far they have never been deep discharged. However they have also never been charged at my end as a 12V standalone set-up. Let's see if it works if I do 2h absorption. Last time I did only 1h. I will post the result.

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Answer 3 · 2018-12-15T14:46:13Z

mnentwig answered · Dec 15, 2018 at 02:46 PM

Johannes, after 4h absorption at 14,2V dc the balancing looks as follows. Balancing seems not work on this Battery. My second Battery is perfectly fine. Any idea what I can do or what could be wrong on this Battery. Thanks, Michael

screenshot-20181215-154204.jpg (383.6 KiB)

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