which battery terminal to disconnect first

The battery terminal to disconnect first is the negative terminal. This is the black terminal on the battery, usually marked with a minus (-) sign. Disconnecting the negative terminal first helps to prevent any electrical shorts and reduces the risk of sparks or accidental contact with the car's metal parts. After removing the negative terminal, the positive terminal (usually red and marked with a plus (+) sign) should be disconnected. When reconnecting the battery, the order is reversed: connect the positive terminal first, then the negative. This practice is widely recommended for safety and to avoid electrical damage while working on automotive batteries.