A distinction is also made between energy conversion efficiency and round-trip efficiency. Energy conversion efficiency refers to the efficiency of each step, such as current conversion processes. Round-trip efficiency, on the other hand, represents the percentage of energy taken from the grid. According to a common industry standard, a BESS is considered to have reached the end of its service life when its actual charging capacity falls below 80%. Charged batteries lose energy over time, even when they are not used. The self-discharge rate measures the percentage of energy lost within a certain period. The optimum operating temperature for most BESS is around 20 degrees Celsius. However, they tolerate temperatures between 5 and 30 degrees Celsius. Some technologies are more tolerant of temperature variations than others. Depending on the climate, this factor can be crucial for the right choice. This figure refers to the voltage a battery can be charged and discharged with safely. The voltage range of an accumulator largely depends on the storage technology and the power electronics.
