On-line estimation early warning method for SOH (State Of Health) of electric vehicle battery pack

The invention discloses an on-line estimation early warning method for an SOH (State Of Health) of an electric vehicle battery pack. The method comprises the following steps: S1, measuring initial maximum capacity of each single battery; S2, acquiring real-time charge and discharge current of each single battery by using a battery management system and estimating an SOC value before and after charge and discharge of each single battery; S3, calculating the SOH value after each charge and discharge of each single battery; S4, judging whether the single battery of which the SOH value is smaller than a first preset threshold value exists in the battery pack, executing a step S6 if the single battery exists, and otherwise, executing a step S5; S5, calculating an average value of the SOH values of all single batteries in the battery pack, judging whether the single battery of which the SOH value differs from the average value for more than a second preset threshold value exists in the battery pack, executing a step S6 if the single battery exists, and otherwise, returning to execute the step S1; S6, triggering the battery management system to enter a protection state and emitting alarm. The method has the advantages of high real-time property, high accuracy, simple implementation mode and low cost and can be widely applied to the monitoring field of the battery pack.