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Use a terminal-cleaning tool to clean the battery terminals.
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A car battery produces an electric current when its terminals are connected to each other to form a circuit. All batteries contain two electrodes (+ and -) and an electrolyte, which produces the chemical reaction that generates a current from the electrodes. "Wet" batteries, like those in cars, contain a liquid electrolyte. Modern car batteries are 12V.
A car battery is designed to produce the strong current needed to turn the starter motor. It does this by using a number of cells linked together. When running, the engine turns an alternator which feeds current back into the battery to recharge it. A car battery contains plates of lead oxide and lead metal, immersed in a sulfuric acid electrolyte. As the battery produces current, both kinds of plate change to lead sulfate. Feeding a current into the battery reverses the chemical reaction.
Car batteries are rated by cold-crank amps (CCA), the minimum electric current (in amps) that a charged 12-volt battery can deliver for 30 seconds at 0 degrees F (brrrrr) without falling below 7.2 volts. The higher the CCA number, the more power it can give you. Of course, you may not need to pay for all that extra power if you live in a warmer climate.
Clean the battery and terminals:
- Identify the terminals. One has a + (positive) symbol on or near it and one has a - (negative) symbol. The cable on one of these two terminals is attached to the engine (ground terminal, usually the negative terminal) and the other goes to the starter.
- Remove the plastic terminal caps, if there are any, and carefully brush away any white powder (corrosion). If the battery cables attach to the battery with a nut, remove the nut and clean the terminal and cable with a wire brush, and then skip to step 6. If the battery uses terminal posts, follow steps 3 through 5.
- Use a wrench to loosen the bolts at the end of the battery cable where it wraps around the ground terminal. Carefully wiggle the cable end up and down until it comes off the terminal; if the end doesn't come off the terminal easily, buy and use a battery terminal puller from the parts store. Then loosen and remove the cable on the other terminal.
- Place the end of the terminal-cleaning tool over each terminal and rotate it a few times. The wire brush inside the tool will clean the terminal post.
- Twist and open the terminal-cleaning tool to expose the round wire brush inside. Insert this brush into the cable ends and rotate the tool to clean the inside of the ends. If the cable ends are broken or the wire is frayed, replace the cable with one of the same length.
- Use an old paint brush to dust away dirt and corrosion from the top and sides of the battery. Make sure the debris doesn't fall on other components or on the car's paint. If the battery is very dirty, remove it from the car and carefully clean it with a solution of a pint of water and a teaspoon of baking soda. Just make sure the solution doesn't get inside the battery.
- Reattach the terminal cables
Charge a battery with a charger:
- Remove all the battery cell caps (if the battery is not maintenance free) and cover the holes with a clean cloth to prevent spattering electrolyte.
- Disconnect the negative battery cable and hook the battery charger cable clamps to the battery posts (positive to positive, negative to negative), then set the charger to 12V if it has a selector and plug in the charger.
- Turn on the charger and check it regularly for the first couple of hours.
- Continue to monitor a higher-amp (faster) charger. Let a trickle charger run for several hours or overnight. A full charge on a trickle charger could take 8 to 16 hours.
- If the battery has removable cell caps, measure the specific gravity with a hydrometer every hour during the last few hours of the charging cycle (follow the instructions on the hydrometer). Consider the battery charged when there's no change in the specific gravity reading for two hours and the electrolyte in the cells is bubbling freely. The specific gravity reading of each cell should be nearly the same; if not the battery probably has one or more bad cells.
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