BATTERY SYSTEM AND BATTERY PACK

Provided are a voltage sensing circuit, a battery pack and a battery system. The voltage sensing circuit includes a first sub-sensing circuit including a light emitting device, and electrically connected in parallel to a battery, and a second sub-sensing circuit including a light receiving device optically coupled to the light emitting device, and electrically isolated from the first sub-sensing circuit. The light emitting device is configured to generate an optical signal in response to a voltage across the light emitting device. The second sub-sensing circuit is configured to output a voltage sensing signal indicating a level of voltage across the battery in response to the optical signal. When the voltage across the battery is equal to a first reference voltage indicating an overvoltage state of the battery, a second reference voltage which is lower than the first reference voltage is applied across the light emitting device. The second reference voltage is lower than a threshold voltage of the light emitting device.