An alarm system for a vehicle charge cord is provided. The alarm system has an armed state and a disarmed state. The alarm system includes a battery, a charge cord sensor, a battery state estimator (“BSE”) module, and an interface module. The battery has state of charge (“SOC”), and is rechargeable to a predetermined level of charge. The charge cord sensor is configured to detect if the vehicle charge cord is connected to or disconnected from a vehicle. The BSE module is configured to monitor the SOC of the rechargeable battery and determine if the battery is charged to the predetermined level of charge. The interface module is in communication with the charge cord sensor and the BSE module. The interface module is configured to switch the alarm system from the armed state to the disarmed state.