BQ25895M

The BQ25895M is switch mode battery charge management and system power path management device for single cell Li-Ion and Li-polymer batteries. It supports high input voltage fast charging and communicates over an I2C serial interface.

To add this library to your project, add the following to the top of your device code:

#require "BQ25895M.lib.nut:1.0.0"

Class Usage

Constructor: BQ25895M(i2cBus [,i2cAddress])

The class’ constructor takes one required parameter (a configured imp I²C bus) and an optional parameter (the I²C address of the BQ25895M. The I²C address must be the address of your chip or an I²C error will be thrown.

Parameters

Parameter	Type	Required	Description
i2cBus	i2c bus object	Yes	The imp i2c bus that the BQ25895M is wired to. The i2c bus must be preconfigured. The library will not configure the bus.
i2cAddress	integer	No	The i2c address of the BQ25895M. Default value is 0x6A

Return Value

None.

Example

local i2c = hardware.i2cKL
i2c.configure(CLOCK_SPEED_400_KHZ);
batteryCharger <- BQ25895M(i2c);

Class Methods

setDefaults()

Initializes the battery charger with default settings.

Parameters

None.

Return Value

None.

Example

// Initializes charger with default settings
batteryCharger.setDefaults();

enableCharging()

Enables the device to automatically perform a charging cycle when a battery is connected and an input source is available.

Parameters

None.

Return Value

None.

Example

// Enables charging
batteryCharger.enableCharging();

disableCharging()

Disables charging capabilities from the device. The device will not charge until enableCharging() is called again.

Parameters

None.

Return Value

None.

Example

// Disables charging
batteryCharger.disableCharging();

setChargeCurrent(milliAmps)

This method sets the fast charge current limit.

The default fast charge current limit is 2048mA.

Parameters

Parameter	Type	Required	Description
currentLimit	Integer	Yes	The desired fast charge current limit in milli Amps (0 - 5056mA)

Return Value

None.

Example

// Sets the fast charge current limit to 5056mA
batteryCharger.setChargeCurrent(5056);

setChargeVoltage(milliVolts)

This method sets the desired battery voltage that the device should charge to.

The default charge voltage is 4352 mV.

Parameters

Parameter	Type	Required	Description
chargeVoltage	Integer	Yes	The desired charge voltage in milli Volts (3840 - 4608mV)

Return Value

None.

Example

// Sets the charge voltage to 4200mV
batteryCharger.setChargeVoltage(4200);

getChargeVoltage()

Returns the target battery charge voltage

Parameters

None.

Return Value

Integer — The voltage in milli volts.

Example

local voltage = batteryCharger.getChargeVoltage();
server.log("Voltage: " + voltage + "mV");

getBatteryVoltage()

Returns the current battery voltage based on the internal ADC conversion.

Parameters

None.

Return Value

Integer — The battery voltage in milli volts.

Example

local voltage = batteryCharger.getBatteryVoltage();
server.log("Voltage: " + voltage + "mV");

getVBUSVoltage()

Returns the VBUS voltage based on the ADC conversion, this is the input voltage

Parameters

None.

Return Value

Integer — The battery voltage in milli volts.

Example

local voltage = batteryCharger.getVBUSVoltage();
server.log("Voltage: " + voltage + "mV");

getSystemVoltage()

Returns the system voltage based on the ADC conversion, this the output voltage which can be used to power other chips in your application

Parameters

None.

Return Value

Integer — The battery voltage in milli volts.

Example

local voltage = batteryCharger.getSystemVoltage();
server.log("Voltage: " + voltage + "mV");

getChargingCurrent()

Returns the measured current going to the battery

Parameters

None.

Return Value

Integer — The charging current in milli Amps.

Example

local current = batteryCharger.getChargingCurrent();
server.log("Current: " + current + "mA");

getChargingStatus()

Returns the charging status

Parameters

None.

Return Value

Integer — see table below for supported values.

Charging Status Constant	Value
BQ25895M_CHARGING_STATUS.NOT_CHARGING	0x00
BQ25895M_CHARGING_STATUS.PRE_CHARGE	0x08
BQ25895M_CHARGING_STATUS.FAST_CHARGE	0x10
BQ25895M_CHARGING_STATUS.CHARGE_TERMINATION_DONE	0x18

Example

local status = charger.getChargingStatus();  
switch(status) {  
	case BQ25895M_CHARGING_STATUS.NOT_CHARGING :  
		// Do something  
		break;  
	case BQ25895M_CHARGING_STATUS.PRE_CHARGE :  
		// Do something  
		break;  
	case BQ25895M_CHARGING_STATUS.FAST_CHARGING :  
		// Do something  
		break;  
	case BQ25895M_CHARGING_STATUS.CHARGE_TERMINATION_DONE :  
		// Do something  
		break;  
}

getChargerFaults()

Returns the possible charger faults

Parameters

None.

Return Value

Table — the possible charger faults

Fault	Type	Description
watchdogFault	Bool	true if watchdog timer has expired
boostFault	Bool	true if VBUS overloaded in OTG, VBUS OVP, or battery is too low
chrgFault	Integer	see table below for possible values
battFault	Bool	true if VBAT > VBATOVP
ntcFault	Integer	see table below for possible values

CHRG_FAULT has an enumerated type to match its output.

Charging Fault	Value
BQ25895M_CHARGING_FAULT.NORMAL	0x00
BQ25895M_CHARGING_FAULT.INPUT_FAULT	0x01
BQ25895M_CHARGING_FAULT.THERMAL_SHUTDOWN	0x02
BQ25895M_CHARGING_FAULT.CHARGE_SAFETY_TIMER_EXPIRATION	0x03

NTC_FAULT has an enumerated type to match its output.

NTC Fault	Value
BQ25895M_NTC_FAULT.NORMAL	0x00
BQ25895M_NTC_FAULT.TS_COLD	0x01
BQ25895M_NTC_FAULT.TS_HOT	0x02

Example

local faults = batteryCharger.getChargerFaults();
server.log("Watchdog Fault =  " + faults.watchdogFault);
server.log("Boost Fault =  " + faults.boostFault);

switch(faults.chrgFault) {  
	case BQ25895M_CHARGING_FAULT.NORMAL:  
		// Do something  
		break;  
	case BQ25895M_CHARGING_FAULT.INPUT_FAULT:  
		// Do something  
		break;  
	case BQ25895M_CHARGING_FAULT.THERMAL_SHUTDOWN:  
		// Do something  
		break;  
	case BQ25895M_CHARGING_FAULT.CHARGE_SAFETY_TIMER_EXPIRATION:  
		// Do something  
		break;  
}

server.log("Battery Fault =  " + faults.battFault);

switch(faults.ntcFault) {  
	case BQ25895M_NTC_FAULT.NORMAL:  
		// Do something  
		break;  
	case BQ25895M_NTC_FAULT.TS_COLD:  
		// Do something  
		break;  
	case BQ25895M_NTC_FAULT.TS_HOT:  
		// Do something  
		break;  

reset()

Restores the devices default settings

Parameters

None.

Return Value

None.

Example

batteryCharger.reset();