SLUUB65B May 2015 – December 2022
It is common for sudden changes in operating conditions such as temperature and discharge load to cause drastic but legitimate changes in the amount of capacity that can be extracted from a given Li-Ion cell or pack. These changes are typically perceived as jumps in reported SOC and can sometimes be alarming to end-equipment users who may not understand how environmental conditions impact available battery capacity. SOC smoothing solves this by gradually equalizing the difference in reported SOC vs "true" SOC over the present cycle. The method for accomplishing this differs, depending on whether or not the current cycle is a charge or discharge. During discharge, the algorithm adds or removes delta charge (deltaQ) from the present coulomb count to accelerate or decelerate change in RemainingCapacity() until it is able to converge to the true value by the time the battery reaches empty. During charge, FilteredFCC() is modified to account for deltas in the true and reported versions of Remaining Capacity, as well as the true and reported versions of Full Charge Capacity. Since FilteredFCC() is continuously modified to ensure SOC convergence in charge, it is not a real determinant of the total available battery capacity and UnfilteredFCC() should instead be referred to for this purpose. The [SmoothEn] bit in Pack Configuration C determines whether unfiltered or filtered values are mapped to RemainingCapacity(), FullChargeCapacity(), and StateofCharge() for reporting to the system host, as shown in the table below.
Pack Configuration C [SmoothEn] | RemainingCapacity() | FullChargeCapacity() | StateOfCharge() |
---|---|---|---|
0 | UnfilteredRM() | UnfilteredFCC() | UnfilteredRM()/UnfilteredFCC() |
1 | FilteredRM() | FilteredFCC() | FilteredRM()/FilteredFCC() |