System and method for battery state of charge determination

A system for determining a state of charge of each of a plurality of battery sections of a rechargeable energy storage system (RESS) of a vehicle, the system comprising:

• the RESS including the plurality of battery sections electrically connected in series;
• an auxiliary power module (APM) in electrical communication with the RESS, wherein the APM is configured to discharge one or more of the plurality of battery sections;
• a controller in electrical communication with the plurality of battery sections and the APM, wherein the controller is programmed to:
• determine a first state of charge of a first battery section of the plurality of battery sections;
• discharge a first amount of charge from the first battery section in response to determining the first state of charge of the first battery section;
• determine a second state of charge of the first battery section in response to discharging the first amount of charge from the first battery section;
• and
• determine the state of charge of each of the plurality of battery sections based at least in part on the first state of charge, the first amount of charge, and the second state of charge.

A method for determining a state of charge of each of a plurality of battery sections of a rechargeable energy storage system (RESS) of a vehicle, the method comprising:

• determining a first state of charge of a first battery section of the plurality of battery sections;
• discharging a first amount of charge from the first battery section within a time period at least in part using an auxiliary power module (APM) configured to provide energy to low-voltage loads of the vehicle in response to determining the first state of charge of the first battery section, wherein the first amount of charge is greater than an amount of charge discharged from a remainder of the plurality of battery sections within the time period;
• determining a second state of charge of the first battery section in response to discharging the first amount of charge from the first battery section;
• and
• determining the state of charge of each of the plurality of battery sections based at least in part on the first state of charge, the first amount of charge, and the second state of charge using a formula:
• SOC
• n
• =
• SOC
• 1
• ,
• 1
• -
• C
• 1
• *
• SOC
• 1
• ,
• 1
• -
• C
• 1
• *
• SOC
• 1
• ,
• 2
• -
• Δ
• ⁢
• Ah
• 1
• ,
• APM
• C
• n
• wherein SOCn is a state of charge of an nth battery section of the plurality of battery sections, SOC1,1 is the first state of charge of the first battery section, C1 is a capacity of the first battery section, SOC1,2 is the second state of charge of the first battery section, ΔAh1,APM is the first amount of charge, and Cn is a capacity of the nth battery section of the plurality of battery sections.