Patent ID: 7026788

Claim:
A battery leakage detection circuit for an electric vehicle comprising: a battery pack including a plurality of batteries that are connected to each other in series; leakage detection resistances R a and R b that are connected in series between a ground, and each of battery terminals of the batteries at two arbitrary locations in the high and low voltage sides; voltage detecting means that detects voltages of the battery terminals in the high and low voltage sides as V g11 (t) and V g12 (t), respectively, at timing t; leakage detection switches SW 1 and SW 2 each of which is connected in series between the leakage detection resistances R a and R b ; a voltage detector that detects a voltage V l11 (t) produced in the leakage detection resistance R a connected to the leakage detection switch SW 1 , when one leakage detection switch SW 1 connected to the battery terminal in the high voltage side is closed at timing t and the other leakage detection switch SW 2 is opened, and detects a voltage V l12 (t) produced in the leakage detection resistance R a connected to the leakage detection switch SW 2 , when the other leakage detection switch SW 2 connected to the battery terminal in the low voltage side is closed at timing t and the one leakage detection switch SW 1 is opened, and a leakage calculator that calculates a combined value R l of the leakage resistances based on the following equation 1 R l = R a V l12 ⁡ ( t 2 ) V g11 ⁡ ( t 2 ) - V g12 ⁡ ( t 2 ) - V l11 ⁡ ( t 1 ) V g11 ⁡ ( t 1 ) - V g12 ⁡ ( t 1 ) - ( R a + R b ) Equation ⁢ ⁢ 1 where t 1 and t 2 are different time values.