BMS application

Battery Management System (BMS) common defines and structs.

Defines

BMS_SWITCH_CHG

BMS_SWITCH_DIS

BMS_SWITCH_PDSG

BMS_SWITCH_PCHG

BMS_ERR_CELL_UNDERVOLTAGE: Cell undervoltage flag.

BMS_ERR_CELL_OVERVOLTAGE: Cell overvoltage flag.

BMS_ERR_SHORT_CIRCUIT: Pack short circuit (discharge direction)

BMS_ERR_DIS_OVERCURRENT: Pack overcurrent (discharge direction)

BMS_ERR_CHG_OVERCURRENT: Pack overcurrent (charge direction)

BMS_ERR_OPEN_WIRE: Cell open wire.

BMS_ERR_DIS_UNDERTEMP: Temperature below discharge minimum limit.

BMS_ERR_DIS_OVERTEMP: Temperature above discharge maximum limit.

BMS_ERR_CHG_UNDERTEMP: Temperature below charge maximum limit.

BMS_ERR_CHG_OVERTEMP: Temperature above charge maximum limit.

BMS_ERR_INT_OVERTEMP: Internal temperature above limit (e.g. BMS IC)

BMS_ERR_CELL_FAILURE: Cell failure (too high voltage difference)

BMS_ERR_DIS_OFF: Discharge FET is off even though it should be on.

BMS_ERR_CHG_OFF: Charge FET is off even though it should be on.

BMS_ERR_FET_OVERTEMP: MOSFET temperature above limit.

BMS_ERR_ALL

Battery Management System (BMS) high-level API.

Defines

NUM_OCV_POINTS

Enums

enum bms_state

Possible BMS states

Values:

enumerator BMS_STATE_OFF: Off state (charging and discharging disabled)

enumerator BMS_STATE_CHG: Charging state (discharging disabled)

enumerator BMS_STATE_DIS: Discharging state (charging disabled)

enumerator BMS_STATE_NORMAL: Normal operating mode (both charging and discharging enabled)

enumerator BMS_STATE_SHUTDOWN: BMS starting shutdown sequence.

enum bms_cell_type

Battery cell types

Values:

enumerator CELL_TYPE_LFP: LiFePO4 Li-ion cells (3.3 V nominal)

enumerator CELL_TYPE_NMC: NMC/Graphite Li-ion cells (3.7 V nominal)

enumerator CELL_TYPE_LTO: NMC/Titanate (2.4 V nominal)

Functions

void bms_init_config(struct bms_context *bms, enum bms_cell_type type, float capacity_Ah)

Initialization of struct bms_ic_conf with typical default values for the given cell type.

Parameters:

bms – Pointer to BMS object.
type – One of enum CellType (defined as int so that it can be set via Kconfig).
capacity_Ah – Nominal capacity of the battery pack.

void bms_state_machine(struct bms_context *bms)

Main BMS state machine

Parameters:

bms – Pointer to BMS object.

void bms_shutdown(struct bms_context *bms)

Switch off MOSFETs and go into the shutdown state

Parameters:

bms – Pointer to BMS object.

void bms_soc_update(struct bms_context *bms)

Update SOC based on most recent current measurement

Function should be called each time after a new current measurement was obtained.

Parameters:

bms – Pointer to BMS object.

void bms_soc_reset(struct bms_context *bms, int percent)

Reset SOC to specified value or calculate based on average cell open circuit voltage

Parameters:

bms – Pointer to BMS object.
percent – 0-100 %, -1 for calculation based on OCV

bool bms_chg_error(uint32_t error_flags)

Charging error flags check

Returns:: true if any charging error flag is set

bool bms_dis_error(uint32_t error_flags)

Discharging error flags check

Returns:: true if any discharging error flag is set

bool bms_chg_allowed(struct bms_context *bms)

Check if charging is allowed

Returns:: true if no charging error flags are set

bool bms_dis_allowed(struct bms_context *bms)

Check if discharging is allowed

Parameters:

bms – Pointer to BMS object.

Returns:

true if no discharging error flags are set

struct bms_context

#include <bms.h>

Battery Management System context information

Public Members

enum bms_state state: Current state of the battery

bool chg_enable: Manual enable/disable setting for charging

bool dis_enable: Manual enable/disable setting for discharging

bool full: CV charging to cell_chg_voltage_limit finished

bool empty: Battery is discharged below cell_dis_voltage_limit

float soc: Calculated State of Charge (%)

float nominal_capacity_Ah: Nominal capacity of battery pack (Ah)

float *ocv_points: Pointer to an array containing the Open Circuit Voltage of the cell vs. SOC. The array must be spaced the same as the soc_points.

float *soc_points: Pointer to an array containing the State of Charge points for the OCV.

const struct device *ic_dev: BMS IC device pointer

struct bms_ic_conf ic_conf: BMS IC configuration applied during start-up.

struct bms_ic_data ic_data: BMS IC data read from the device.