To accurately determine life of a battery with respect to an onboard unit and a program.

The onboard unit 1 to which a power supply voltage is supplied from an onboard battery 15 includes an input unit 12 for inputting a threshold for the fluctuation range ΔV of the power supply voltage and a control unit 11 which compares the fluctuation cycle of the power supply voltage to the fluctuation cycle of the terminal voltage of a winker 17 to which the power supply voltage is supplied from the onboard battery 15, and determines the life of the onboard battery 15 on the basis of the fluctuation range ΔV of the power supply voltage and the threshold input by the input unit 12 when the fluctuation cycle of the power supply voltage and the fluctuation cycle of the terminal voltage of the winker 17 are synchronized with each other.

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