Good car maintenance includes checking your battery regularly. A car battery that's kept clean and filled with water should last a long time. Pay special attention to the battery's trouble spots, shown in Figure 1.
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Figure 1: The parts of the battery that you want to pay attention to during a regular check. |
To check your battery, follow these steps:
1. If you have a battery with removable caps or bars on top, remove them. (See Figure 2.)
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Figure 2: Battery covers with removable caps or bars. |
2. If your battery isn't sealed, look inside the battery.
If the battery is sealed, skip to Step 4.
3. If the liquid inside the battery doesn't reach the tops of the plates, add distilled water or water with a low mineral content until it covers them.
Be very careful not to add liquid past the top of the fins inside the battery.
4. If you see powdery deposits on the terminals, clean them off.
The cruddy deposits on the terminals are made by battery acid. Before you clean it off, remove the cables from the positive terminal and negative terminal by undoing the nut on each cable clamp and wiggling the cable until the clamp comes off the terminal post.
Always remove the cable clamp from the negative terminal first. (It's the one that's marked with a – sign.) Replace the positive cable first and the negative cable last. If you attempt to remove the positive clamp first and your wrench slips and touches something metal, your wrench can fuse to the part like an arc welder.
Clean the deposits off the terminal posts and cable clamps: Sprinkle on baking soda straight from the box, dip a toothbrush or disposable nonmetallic brush in water, and scrub.
If your cables and clamps won't clean up completely, rotate a round battery terminal cleaner brush (see Figure 3) on each terminal to shine it up and ensure a solid electrical connection. Clean the insides of the cable clamps with the clamp cleaner that is usually sold with the terminal brush. If you can't find these brushes, use a soapless steel wool pad.
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Figure 3: A battery terminal brush and clamp cleaner. |
5. Dry everything with a clean, disposable, lint-free rag.
6. To prevent corrosive deposits from forming again, coat the terminals with grease or petroleum jelly.
7. Examine the battery cables and clamps for fraying or corrosion.
If the damage looks extensive, replace the cables and clamps; otherwise, the battery may short-circuit and damage onboard computers.
Take these precautions: Tie the cables back while working on the battery so that they don't flop back over onto the terminals. Always remove the negative cable if you plan to work on wiring under the hood. Don't allow anything made of metal to connect the terminal posts; this can damage the battery. If the cables are connected to the posts at the time, you could destroy the onboard computers.
8. If you've been having trouble starting your car, if your headlights seem dim, or if the battery is old and has bars or caps that you can remove and look inside, buy a battery tester (see Figure 4) and use it to check whether the battery acid concentration is high enough.
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Figure 4: Battery tester. |
You simply draw some of the battery fluid into the tester and look at the floating balls inside it. A scale on the tester tells you the condition of the battery fluid. If you get a very low reading, get the battery refilled and recharged at a service station. If they tell you that your battery should be replaced, replace it.
If you have a sealed battery and you own or can borrow a voltmeter, attach it across the battery terminals (red to positive and black to negative). With all accessories off and the battery at 70 degrees Fahrenheit, the voltage reading should be 12.6 volts or slightly lower at lower temperatures. Or just have your local service station test the battery.
9. Check the battery case and the terminals.
If you see major cracks in the battery case or obvious terminal damage, the battery should be replaced regardless of its electrical performance.
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