Absorption voltage can’t be reached

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praxe asked Dec 25, '23

Absorption voltage can’t be reached

Hi guys, I have a VictronConnect multiplus 2 12V 3000VA that is hooked up to two Ultimatron 150Ah lifepo4 batteries.

I have set the absorption voltage according to the battery specifications to 14.6V. Nevertheless the BMS kicks in at around 14.2V and stops the charging the process. All the cells seem to be pretty good balanced.

The multiplus stays at 14.6V and does not drop down to float voltage (set at 13.8V).

The batteries are new, do they need to get a few cycles until they reach full capacity?

thanks in advance

br lukas

Multiplus-II lifepo

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Answer 1 · 2023-12-26T09:53:02Z

thanar answered · Dec 26, 2023 at 09:53 AM

If the BMS is kicking in, then there is a cell that goes higher than it's supposed to. How to you know that "the cells are pretty good balanced"? Do you have some insight on the BMS data?

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Answer 2 · 2023-12-26T12:37:45Z

praxe answered · Dec 26, 2023 at 12:37 PM

Yes I can see the cell voltage via the Ultimatron app. They are all in a range of +/- 0.005V. Maximum delta between the highest and the lowest is 0.008V

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Answer 3 · 2023-12-26T13:01:21Z

rikhf answered · Dec 26, 2023 at 01:01 PM

How is the charging process stopped? By switching off the BMS or by telling the Victron system to reduce charge current?

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Answer 4 · 2023-12-26T21:55:41Z

praxe answered · Dec 26, 2023 at 09:55 PM

Via the BMS. The Victron system stays at 14.6V, I guess until the maximum absorption time is reached. Then the system stays at float voltage 13.6V.

Battery voltage drops from 14.2V to 13.6V.

SoC from the batteries also slowly drops from 100% to 97%, even when the multiplus is still in charging/float mode.

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