Some chargers, such as the BQ2515x family of Linear Charger BMUs, include an ADC; the BQ2515x’s ADC directly reports battery voltage from 2 V to 5 V. Other chargers, such as the BQ25120 includes a battery voltage monitor which reports battery voltage as a percentage of battery regulation voltage. Almost all I2C chargers with power path management include a programmable Battery UnderVoltage Lock-out (BUVLO) protection feature which can be used for the purpose of getting an estimate of battery voltage.

The feature can first be triggered when a BUVLO fault is reported by the charger. This indicates that battery voltage has dipped below the BUVLO threshold, this is when one can begin to check for low voltage. If the BUVLO setting is not the lowest value, disabling charge then decreasing to the lowest BUVLO setting can allow the system to identify if the battery has fallen to a critically discharged level.

Most chargers are disabled if the battery drops below BUVLO. Because of this, it is important to note that using the BUVLO as a voltage monitor is requires an input adapter. Otherwise this may inadvertently disable the device. Note that the battery voltage can potentially be equal to the BUVLO voltage plus the BUVLO hysteresis value since a Battery UVLO flag can only be cleared once battery voltage rises above the hysteresis added voltage.