Q: How to disconnect and reconnect a Nissan Versa's battery?A: Some vehicle systems require continuous battery voltage to work such as the alarm system and power door locks and there are others that need it to keep control unit memory as presets of radio stations and Powertrain Control Module. In order to prevent getting locked in the vehicle, it is necessary to take out the key or keyless entry fob before disconnecting the battery. It is possible to run into these issues by using memory saver devices which are connected to an extra battery and plugged into the cigarette lighter. For ensuring no accidental contact with battery terminal, when detaching battery, loosen cable end bolt and separate the cable end. On reattaching a battery, always begin with attaching the positive cable then follow by negative cable. After that there are some re-learn procedures such as steering angle sensor position learning, idle air volume learning, accelerator pedal released position learning, throttle valve closed position learning, power window initialization and anti-pinch feature, sunroof memory and anti-pinch feature, radio presets, navigation system adjustment must be performed. However it is possible to avoid these procedures if a memory saver was used.