A non-transitory computer-readable medium having instruction stored thereon, which when executed by a processor, cause the processor to perform a method of determining a relative state of charge of a battery coupled to a surgical instrument used during a surgical procedure, the method comprising:
- detecting an input at a user interface of the surgical instrument;
- in response to the detected input at the user interface, matching a discharge profile to the detected input, the discharge profile corresponding to a discharge curve representing current discharge over time;
- and
- identifying a relative state of charge from the discharge curve based on a usage of the surgical instrument during the surgical procedure.