Internal short circuit (ISCr) is one of the major safety concerns of lithium batteries, and may result in thermal runaway of batteries. The detection of ISCr in battery is critical for preventing thermal runaway and promoting electrical vehicle safety. In this research, the electrical characteristics of the ISCr of lithium ion batteries are analyzed through the battery equivalent circuit model (ECM). An ISCr detection method is developed based on battery consistency inside the battery pack. The proposed ISCr detection method adopts the recursive least square (RLS) algorithm basing on the mean-difference model (MDM). The proposed method first estimates the basic parameters of the MDM, then calculates the characteristic parameters, such as the differential of the voltage and the fluctuation function of the internal resistance, derived from the basic parameters of the MDM. These characteristic parameters largely vary from their normal values once ISCr occurs, thereby enable the battery management system to achieve ISCr detection. The effectiveness of the proposed method is validated through experiments. The proposed ISCr detection method is integrated into battery management system (BMS) of vehicles and yields satisfactory performance.