Vehicle-mounted battery diagnosis method and vehicle-mounted battery diagnosis device

The invention provides a vehicle-mounted battery diagnosis method. The method comprises the steps that firstly, a state-of-charge threshold interval [a, b] of a vehicle-mounted battery, a threshold N of the number of times of abnormality of the vehicle-mounted battery, and a first power threshold Y1 and a second power threshold Y2 of the vehicle-mounted battery are set; then, after the vehicle is powered on, the number n of times of abnormity of the vehicle-mounted battery before the vehicle is powered on is read; then, n is compared with N, and whether the vehicle-mounted battery has an over-charge or over-discharge fault or not is diagnosed; further, if no fault exists temporarily, the current charge state c of the vehicle-mounted battery is obtained and compared with [a, b], and if c is smaller than a, the first power y1 of the vehicle-mounted battery in the first time period is obtained; if c is greater than b, the second power y2 of the vehicle-mounted battery in a second time period is acquired; and fin