Coulombic or Faradic efficiency
We define the Coulombic (or Faradic) efficiency as the ratio of the cumulated discharging current to the charging current. This ratio is usually rather high, of the order of 97% for Lead Acid batteries.
For the Li-Ion technologies, we don't have explicit data. We suppose a value of 96%, for approaching the global energetic efficiency of 90-95% reported by some few manufacturers.
This parameter is due to the Electrochemical conversion current efficiency.
The coulombic efficiency should not be confused with the battery energy efficiency, which includes also other losses, mainly the resistive losses due to the internal resistance, which increases the charging voltage and decreases the discharging voltage.
NB: In lead-acid batteries we have a "gassing" phenomenon, due to the dissociation of the water molecules when the battery is overcharged. This consumes an additional current, which is accounted independently (not in the coulombic efficiency) in the PVsyst model.