Battery lifetime expectancy - Total energy stored?

[Sylvai Vitali]

Hello,

PVSyst automatically gives the total amount of energy stored in a battery during its life, which is very interesting (it would be even better with the latest Huawei Luna battery models).

How is battery life defined?
In the example below, can I assume that after 114 MWh, the battery is completely dead?

And are these kWh estimated on the AC side of the battery's inverter, taking into account the inverter's efficiency?

Thanks in advance for your help,
Sylvain Vitali

 

[André Mermoud]

The capacity slightly decreases when using the battery. The battery life (number of cycles specified by the manufacturer) is defined as the situation when the capacity drops below a given threshold.

Traditionnally, this limit was usually 80%. Since some years, several manufacturers consider a drop down to 70% of the initial capacity. This is not always mentioned on the datasheets.

The discrimination between input or output of the battery (efficiency, around 5%) doesn't make much sense as the uncertainty on the number of cycles is much much higher.