Voltage peaks during absorption phase on a 120/20 solar charge controler

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pvtom asked May 2, '24

Voltage peaks during absorption phase on a 120/20 solar charge controler

I have two 400W solar panels in parallel and 3 x 24V 25Ah Lifepo4 (parallel) on a 120/20 charge controller. Settings are Victron standard for Lifepo4.

As soon as the absorption phase starts, I observe Voltage peaks up to 34V.

I think the controller is working against the Lifepo4 BMS cut of at 30V.

Lifepo4 manufacturer suggest absorption voltage beween 28.8 to 29.2 Volts. I fear if I lower the absorption voltage further than the standard setting of 28.4V the internal BMS will never balance the battery.

What can I do?

Thanks for your help

overvoltage

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Answer 1 · 2024-05-19T16:06:19Z

Nicolas Trejahn answered · May 19 at 04:06 PM

Those peaks appear to be a little excessive, I agree. I have tried two methods: lowering the threshold to 28,00 V. Yes, it might have an effect on balancing. However my batteries are at 100% at 11 am every day so I think I still get into balancing mode often enough. The second method is to set the Absorption duration to "Adaptive" in the expert settings, resulting in fewer or shorter Absorbtion phases.

Might not be what you were looking for though.

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