The high currents drawn by the starting system (starter) mean that the voltage drop in the wires must be minimal. Voltage drop caused by resistance in the wires and their connections reduces the voltage required to crank the engine and even to operate the computer. Check the entire length of the wires coming from the battery, as well as all clamps and connections. Check the positive and negative terminals and wires for corrosion and loose connections. Corrosion on battery terminals typically appears as a light, loose powder (arrow). Clean or replace the terminals if necessary.
Clean the wire terminals with a special brush and contact cleaner, as well as a solution of baking soda. When cleaning the wire clamps, you want to remove all the corrosion inside the cone-shaped holes, but be careful not to remove too much material.
Regardless of the tool used to clean the battery contacts, they must be cleaned to a shine.
Wash the contacts and the top of the battery case with the baking soda solution, but be careful not to let any of it get inside the battery.
When cleaning the wires, contacts, and battery case, use rubber gloves and safety glasses to prevent the solution from getting on your hands, eyes, or clothing. Even diluted electrolyte can burn through clothing, so it is better to wear old clothes.
If the contacts are heavily corroded, clean them with a brush. Rinse all cleaned surfaces thoroughly with clean water.
Caution: Although the wires can be repaired and there are replaceable contacts, it is better to replace the wires completely. New wires have connections that are more sealed and more resistant to corrosion, and their service life is longer than that of repaired ones.
Early-model batteries with removable cell caps should be checked periodically to ensure the correct electrolyte level is present in the cells.
Caution: On a maintenance-free battery with removable plugs, it is recommended to check the electrolyte level regardless of the manufacturer's recommendations. If the electrolyte level in one of the cans is low, you need to add distilled water.