Patent ID: 8854047

Claim:
A voltage monitor for monitoring a voltage of a battery based on a monitor threshold value and for diagnosing the voltage of the battery based on first and second diagnostic threshold values, the voltage monitor comprising: a first means that obtains a first relative correlation between the voltage of the battery and any one of the monitor threshold value and the first diagnostic threshold value, and outputs first information indicative of the obtained first relative correlation; a second means that obtains a second relative correlation between the voltage of the battery and any one of the monitor threshold value and the second diagnostic threshold value, and outputs second information indicative of the obtained second relative correlation; a threshold switching means that switches a threshold used by the first means to the monitor threshold value and a threshold used by the second means to the monitor threshold value when carrying out the monitor, and that switches the threshold used by the first means to the first diagnostic threshold value and the threshold used by the second means to the second diagnostic threshold value that is a same value as the first diagnostic threshold value when carrying out the diagnosis; and a fault detecting means that: receives the first information outputted from the first means and the second information outputted from the second means after the first and second threshold values have been switched to the same value; and detects that there is a fault in a threshold switched by the threshold switching means if the first information of the first means is different from the second information of the second means.