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bluefab avatar image
bluefab asked

BYD LVS - Strange increase of "min/max voltage" difference after 100% charge

Hello everybody,

I have an offgrid system, running for 1 year, made of a 8kWh BYD LVS battery, a MPPT RS450-100, and a Multiplus II 5000 VA.
Everyday, after the battery reaches 100%, I observe a strange increase of the max cell voltage, during hours :

strange-min-max-voltage.pngIs it normal ? Does anyone have an idea of what happens ? The BMS should be balancing the cell's voltage instead, no ?

Thank you very much for your help

BYDbattery system voltage
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3 Answers
Alexandra avatar image
Alexandra answered ·

@BlueFab

Are you getting any battery warnings?

If not then don't stress about it.

The system is rebulking the batteries during sunny hours which is also normal. And it is staying within the request 56.5v of the bms cvl. So also normal.

I have seen the 3.6v on quite a few different BYD systems. They seem to allow it in software.

Sometimes the graphs render a bit strange when zoomed out so much. Look at a 24 hour period at a time.

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bluefab avatar image
bluefab answered ·

Thank you for your answer

Yes I get high voltage warnings, once per day, several day per month, when the battery reaches 100%, like this one :

probleme-sur-tension.png

I made a zoom in the curves :

strange-min-max-voltage-2.png

So it's normal if the difference increases after the 100% ? I don't understand why, some cells are left on the side by the BMS while others continue to gain voltage, even after complete charge ?


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micmak avatar image
micmak answered ·

I have the same issue with my setup. I have a Quattro with a Fronius on AC OUT and 2 MPPT, and a BYD LVS (8 modules). I get this warning almost every day. The only workaround is to go to DVCC and set "limit managed battery charged voltage" to 55. The battery will reach 99% and you won't have the alarm, but the behavior is the same:

1680007136336.png


Mine reach 3.7x sometimes if I don't set a limit, I am not sure why.


1680007136336.png (25.5 KiB)
1 comment
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joolster avatar image joolster commented ·

Conversed with BYD support - they said this is not an issue as the voltage is within permitted operating parameters


You can also avoid the alarm by setting the SOC to below 100%, say 99% - one way to do this is via nodered as otherwise the GUI only allows increments of 5% for SOC target

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