Car batteries are 12V current and filled with corrosive acid that eats clothing and burns skin; therefore, you need to use caution when handling these batteries. Before you even begin to disconnect your battery, you should have a pair of safety goggles and a pair of long-sleeved rubber gloves to wear to protect yourself. Battery acid burns to the eyes are not only painful, but extremely serious, warranting a trip to the emergency room.
Look for the symbols you need to know. The positive terminal will either say POS or will show a positive symbol (+); the negative terminal will read NEG or show a negative symbol (-). Green and white ashy substances on and around the terminals and wires are corrosion and must be removed before proceeding to the next step. To remove corrosion, mix a solution of baking soda and water and pour over both terminal ends. The mixture will fizz and bubble and this is normal. Repeat this until both terminals look cleaned up. Wipe up mess around the terminals with a paper towel and discard in the trash.
Pick up the 1/2-inch wrench and place it on Unscrew the nut at the side of the negative terminal by turning it with a 1/2-inch wrench. When the terminal loosens enough to remove it from the negative post, stop and twist off the terminal without removing the nut all the way. This prevents losing the nut.
Repeat Step 2 on the positive terminal after you have lifted the negative terminal off the negative post. Be extra careful not to let the positive terminal touch any metal part of the car. When both posts of the battery are free of terminal ends, pour more baking soda mixture on those posts and scrub them with a wire brush until shiny. This will make a good contact and ensure proper starting abilities. Next use a wire brush to clean inside and on top of each terminal end to ensure good contact with posts when placed back on.
Always use caution when working around a car battery