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ndl avatar image
ndl asked

BYD battery question

Good morning @BYD_service

I see that you are the expert on the BYD and would appreciate if you could answer a few queries.

I have a Victron Multiplus II with the BYD 2.56kWh battery. The battery never seems to reach 100% SOC.


The MP-II is grid tied as backup only for grid failures (ESS). It charges correctly and quickly but doesnt reach the 100%.



Although the charging current shows 25A it actually charges at ±32A looking at the graphs.


Considering that my system is for grid backup only (no solar), is there any recommendations with regards to cycling, DOD etc that you would recommend i.e. discharge to 30% SOC once a month or is it fine to just let it be.


Thank you

Kind regards

Nico

Multiplus-IIBYD
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gumalu avatar image gumalu commented ·

I have a question

Is your Multiplus II going in to Float mode with this configuration?

Thanks

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byd-service answered ·

Hello,

Regarding the first question, it is not critical that the battery shows 100% SOC as long as it calibrates the SOC, which as your system is already reaching 55.2v it should be doing correctly. I´m looking with our engineers in which circumstances it shows 99% instead but in any case if it calibrates it is full.


Regarding the second question. Ideally, you wouldn´t keep them full all the time as this puts them under some mechanical stress. I see you´re letting them go down by about 20% which is more than fine. As you are charging the batteries from the grid I wouldn´t ask you to spend money on cycling the batteries just for the sake of cycling them.

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ndl avatar image ndl commented ·

Thank you for the response @BYD_service.


I don't mind cycling the batteries once a month or so if it will prolong the life of the batteries (even it is from the grid).

What is the maximum duration you would recommend the batteries spend at full? If there is no grid failures it could be for a prolonged period that they will remain full. What would the optimal solution be in this case, cycle the batteries or lower the SOC.


Regards

Nico

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byd-service avatar image byd-service ndl commented ·

Hello,


Don't worry about this point as the BMS will protect the batteries so any losses due to this point will not be noticeable.

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