A battery monitoring system, comprising: a battery for an aerial vehicle, the battery comprising a plurality of stacked cells; an ultrasonic sensor configured to emit ultrasonic waves toward the battery, the ultrasonic sensor further configured to receive echoes of emitted ultrasonic waves reflected back from the battery; and a control system in communication with the ultrasonic sensor and configured to at least: instruct the ultrasonic sensor to emit ultrasonic waves toward one or more surfaces of the battery; instruct the ultrasonic sensor to receive echoes of the emitted ultrasonic waves reflected back from the one or more surfaces of the battery; process the emitted ultrasonic waves and the received echoes of emitted ultrasonic waves to determine an actual time of flight of the ultrasonic waves; determine a change in a dimension associated with the one or more surfaces of the battery based on a comparison between the actual time of flight and a reference time of flight, wherein the reference time of flight is a known time of flight of emitted ultrasonic waves reflecting back from a wall or a surface of an electrochemical cell of the battery known from previous measurements; and calculate a state of charge or a state of health of the battery by comparing the determined change in the dimension to changes in an equivalent dimension of one or more other batteries, wherein the state of charge is calculated by comparing the determined change in the dimension to a known dimension of the battery at a known state of charge, and wherein the state of health of the battery is a condition of the battery relative to its ideal specifications and is calculated by comparing the determined change in the dimension of the battery over time with respective changes in dimension of other similar batteries over time and/or known changes in dimension of other similar batteries having ideal specifications. a battery for an aerial vehicle, the battery comprising a plurality of stacked cells; an ultrasonic sensor configured to emit ultrasonic waves toward the battery, the ultrasonic sensor further configured to receive echoes of emitted ultrasonic waves reflected back from the battery; and a control system in communication with the ultrasonic sensor and configured to at least: instruct the ultrasonic sensor to emit ultrasonic waves toward one or more surfaces of the battery; instruct the ultrasonic sensor to receive echoes of the emitted ultrasonic waves reflected back from the one or more surfaces of the battery; process the emitted ultrasonic waves and the received echoes of emitted ultrasonic waves to determine an actual time of flight of the ultrasonic waves; determine a change in a dimension associated with the one or more surfaces of the battery based on a comparison between the actual time of flight and a reference time of flight, wherein the reference time of flight is a known time of flight of emitted ultrasonic waves reflecting back from a wall or a surface of an electrochemical cell of the battery known from previous measurements; and calculate a state of charge or a state of health of the battery by comparing the determined change in the dimension to changes in an equivalent dimension of one or more other batteries, wherein the state of charge is calculated by comparing the determined change in the dimension to a known dimension of the battery at a known state of charge, and wherein the state of health of the battery is a condition of the battery relative to its ideal specifications and is calculated by comparing the determined change in the dimension of the battery over time with respective changes in dimension of other similar batteries over time and/or known changes in dimension of other similar batteries having ideal specifications. instruct the ultrasonic sensor to emit ultrasonic waves toward one or more surfaces of the battery; instruct the ultrasonic sensor to receive echoes of the emitted ultrasonic waves reflected back from the one or more surfaces of the battery; process the emitted ultrasonic waves and the received echoes of emitted ultrasonic waves to determine an actual time of flight of the ultrasonic waves; determine a change in a dimension associated with the one or more surfaces of the battery based on a comparison between the actual time of flight and a reference time of flight, wherein the reference time of flight is a known time of flight of emitted ultrasonic waves reflecting back from a wall or a surface of an electrochemical cell of the battery known from previous measurements; and calculate a state of charge or a state of health of the battery by comparing the determined change in the dimension to changes in an equivalent dimension of one or more other batteries, wherein the state of charge is calculated by comparing the determined change in the dimension to a known dimension of the battery at a known state of charge, and wherein the state of health of the battery is a condition of the battery relative to its ideal specifications and is calculated by comparing the determined change in the dimension of the battery over time with respective changes in dimension of other similar batteries over time and/or known changes in dimension of other similar batteries having ideal specifications.