Patent ID: 8841915

Claim:
A battery voltage monitoring apparatus comprising: pairs of positive side and negative side detection terminals provided respectively corresponding to positive and negative electrodes of battery cells connected in series to form a battery pack; an RC filter circuit interposed between the positive and negative electrodes of the battery cells and the pairs of the positive side and negative side detection terminals; and a detection means for detecting a cell voltage of each of the battery cells applied across a corresponding one of the pairs of the positive side and negative side detection terminals, for each adjacent two of the battery cells, the positive electrode of the battery cell on the higher voltage side and the negative electrode of the battery cell on the lower voltage side being commonly connected to a common terminal provided in the RC filter circuit, the common terminal being branched into a first branch connected to one end of a first resistor as a component of the RC filter circuit and a second branch connected to one end of a second resistor as a component of the RC filter circuit, the first resistor being connected to a corresponding one of the positive side detection terminals at the other end thereof, the second resistor being connected to a corresponding one of the negative side detection terminals at the other end thereof a capacitor being connected across a corresponding one of the pairs of the positive side and negative side detection terminals as a component of the RC filter circuit, wherein when one of two pairs of the positive side and negative side detection terminals of each adjacent two of the battery cells forms a first pair and the other of the two pairs forms a second pair, the battery voltage monitoring apparatus further comprises: a switch device for making a short circuit between the positive side detection terminals of the first and second pairs and between the negative side detection terminals of the first and second pairs; and a determination means for determining whether or not a circuit abnormality is present between the battery pack and the switch device based on a voltage applied across the positive side and negative side detection terminals of at least one of the first and second pairs when the switch device is turned on, the determination means being configured to determine whether or not a wire breakage is present between the battery pack and the switch device based on comparison between the applied voltage and a wire breakage determination threshold set to a value higher than 0 V and lower than the cell voltage divided by the first and second resistors.