Static state of charge correction techniques for lithium iron phosphate battery systems

A static state of charge (SOC) correction method for a lithium iron phosphate (LFP) battery system of an electrified vehicle, the static SOC correction method comprising:

• obtaining and storing, by a controller of the electrified vehicle and in a memory accessible by the controller, a calibrated look-up table relating (i) power-off times of the electrified vehicle and temperatures of the LFP battery system to (ii) self-discharge rates of the LFP battery system, wherein the self-discharge rates of the LFP battery system corresponds to periods where an active C-rate discharge of the LFP battery system is not commanded;
• detecting, by the controller, a power-off of the electrified vehicle;
• in response to detecting the power-off of the electrified vehicle, (i) determining, by the controller, an initial SOC of the LFP battery system, (ii) initiating, by the controller, a power-off timer, and (iii) initiating, by the controller, a periodic temperature measurement of the LFP battery system;
• after detecting the power-off of the electrified vehicle, detecting, by the controller, a subsequent power-on of the electrified vehicle;
• in response to detecting the subsequent power-on of the electrified vehicle, (i) stopping, by the controller, the power-off timer, (ii) determining, by the controller, an average of the periodic temperature measurements of the LFP battery system to obtain a measured temperature of the LFP battery system, and (iii) accessing, by the controller via the memory, the calibrated look-up table to determine an actual self-discharge rate of the LFP battery system based on a value of the power-off timer and the measured temperature of the LFP battery system;
• and
• determining, by the controller, a corrected SOC for the LFP battery system by determining an SOC change based on the determined actual self-discharge rate and subtracting the SOC change from the initial measured SOC.