A method of determining a state of health of a generator battery and an ability of the battery to supply a generator starter motor with start-up energy, the method being implemented in a monitoring system including an electrical meter electrically coupled to the battery, the method comprising: building reference measurements of battery voltage over time for generator starts, building the reference measurements of battery voltage over time for generator starts comprising defining regions of the reference measurements of battery voltage over time, each of the regions having a duration and a magnitude of voltage change; capturing measurements of battery voltage over time during a generator start operation, capturing the measurements of battery voltage over time comprising defining regions in the captured measurements of battery voltage over time corresponding to the regions defined in the reference measurements of battery voltage over time; characterized in that the method further comprises building a mathematical model describing the reference measurements of battery voltage over time in the regions, wherein building the mathematical model comprises defining one or more mathematical equations describing the measurements of battery voltage over time in the regions defining statistical process control limits about the one or more mathematical equations; and issuing a warning responsive to the captured measurements of battery voltage over time differing from the mathematical model in corresponding one or more of the regions by more than a predetermined amount wherein the warning is issued responsive to data points in the captured measurements of battery voltage over time violating a statistical process control rule relative to the statistical process control limits. building reference measurements of battery voltage over time for generator starts, building the reference measurements of battery voltage over time for generator starts comprising defining regions of the reference measurements of battery voltage over time, each of the regions having a duration and a magnitude of voltage change; capturing measurements of battery voltage over time during a generator start operation, capturing the measurements of battery voltage over time comprising defining regions in the captured measurements of battery voltage over time corresponding to the regions defined in the reference measurements of battery voltage over time; characterized in that the method further comprises building a mathematical model describing the reference measurements of battery voltage over time in the regions, wherein building the mathematical model comprises defining one or more mathematical equations describing the measurements of battery voltage over time in the regions defining statistical process control limits about the one or more mathematical equations; and issuing a warning responsive to the captured measurements of battery voltage over time differing from the mathematical model in corresponding one or more of the regions by more than a predetermined amount wherein the warning is issued responsive to data points in the captured measurements of battery voltage over time violating a statistical process control rule relative to the statistical process control limits.