See Figures 1, 2, 3, 4 and 5
Loose, dirty, or corroded battery cable terminals are a major cause of no-start. Every 3 months or so, disconnect the battery cables and clean them, giving them a light coating of petroleum jelly when you are finished. This will help to retard corrosion. After cleaning, make sure that the vinyl or rubber protector on the positive terminal covers the terminal completely.
Check the battery cables for signs of wear or chafing and replace any cable or clamp that looks marginal. Battery terminals can be easily cleaned and inexpensive terminal cleaning tools are an excellent investment that will pay for themselves many times over. They can usually be purchased from any well equipped auto store or parts department. Side terminal batteries require a different tool to clean the threads in the battery case. The accumulated white powder and corrosion can be cleaned from the top of the battery with an old toothbrush and a solution of baking soda and water.
Check the condition of the battery tray and any hold-down hardware. The battery is supposed to be held in a stationary position; loose, rusted or missing hold-down hardware will result in battery movement which could damage the battery, its cables and/or clamps.
Unless you have a sealed, maintenance-free battery, check the electrolyte level and test its specific gravity at each battery cell. Be sure that the vent holes in each cell cap are not blocked by grease or dirt. The vent holes allow hydrogen gas, formed by the chemical reaction in the battery, to escape safely.
Some batteries are equipped with a built-in charge indicator, located on top of the battery case. If the indicator is blue or green, there is sufficient electrolyte; if no color is visible, check the level and add clean water as necessary.
Some maintenance-free batteries have sealed tops which do not allow the addition of water.
It is ideal to use distilled water in your battery to minimize mineral deposits on the lead (or other type of metal) plates. However, if the water in your area is reasonably soft, you can simply add clean tap water.
See Figures 6 and 7
Check the fluid level in the battery at least once a month and more frequently in cold weather. Check the battery first, if the vehicle's ammeter indicates an abnormality.
The electrolyte level should be 0.4-0.8 in. (10-20mm) above the plates in each cell. Add distilled or clean, reasonably soft tap water, if necessary. Do not overfill. If the temperature is below 32°F (0°C), run the engine for five minutes after adding water so the charging action will mix newly added water with the battery acid and prevent freezing.
CABLES AND CLAMPS
When battery removal or other circumstances require the cables to be disconnected from the battery, begin with the negative cable. Use the correct size open end wrench to loosen the nut on the cable clamp (top post batteries) or the bolt on the cable end (side terminal batteries). If you encounter corrosion, use a little penetrating oil to avoid rounding off the edges of the fasteners. After loosening the appropriate fastener, lift the cable clamp or cable end from the battery terminal. If you encounter resistance with top post batteries, try gently turning the clamp as you lift it, but be careful not to damage the battery terminal. Clean the battery posts and cable clamps or ends, as necessary.
On top post batteries, the positive cable clamp may be covered by a protective hood, which must be moved aside for terminal access.
Check the cables at the same time that the terminals are cleaned. If the cable insulation is cracked or broken, or if the ends are frayed, the cable should be replaced with a new cable of the same length and gauge.
Before connecting the cables, loosen the battery hold-down clamp or strap, remove the battery and check the battery tray. Clear it of any debris, and check it for soundness. Rust should be wire brushed away, and the metal given a coat of anti-rust paint. Replace the battery and tighten the hold-down clamp or strap securely. Be careful not to overtighten, however, as you might crack the battery case.
When it is time to connect the cables to the battery, attach the positive cable first and the negative cable last. On top post batteries, do not hammer on the clamps to install. Tighten the clamps securely, but do not distort them. If the battery cable is OK, but its clamp is worn or damaged, you may want to install a replacement clamp. Give the clamps and terminals a thin external coat of grease after installation, to retard corrosion. On top post batteries, cover the positive terminal and cable clamp with the cable's vinyl or rubber protective hood, if so equipped.
See Figures 8 and 9
Specific gravity is a good indication of the battery's state of charge. Check the specific gravity of each cell's electrolyte with a hydrometer. To use a hydrometer, remove a vent cap and insert the tip of the hydrometer into the electrolyte. Squeeze the bulb on the hydrometer so that a sufficient amount of fluid is drawn into the tester. Note the specific gravity of the electrolyte, as indicated by the hydrometer. (One common, inexpensive type of hydrometer uses a series of floating balls, another type uses a float, and a third type uses a pivoting pointer. Follow the instructions for your particular type.) After noting the reading, return the fluid to the cell from which it came, and repeat this procedure for the remaining cells. If all readings do not fall within the specified range for the given temperature, recharge or replace the battery as necessary. Be sure to check all of the individual cells. Often when a battery fails, only one of its cells has an abnormal reading.
Some maintenance-free batteries have a sealed top which prohibits the use of a hydrometer. Instead, such batteries often have have a built-in charge indicator whose color indicates the battery's condition. On these batteries, a blue or green indicator normally represents a normal charge condition.
The cold cranking amps (CCA) of a battery indicates available starting power at a given temperature (generally 32°F/0°C). Although there is a rough correlation between engine size and battery power requirements, the actual needs will depend, in part, on the extent of power accessories, the local climate and one's driving habits. As a general rule of thumb, the CCAs of a replacement battery should match or exceed those of the original battery. However, since electrical wiring develops increased resistance with age, it may be advisable to select a replacement battery with CCAs at least 10% higher than the original.
The reserve capacity of a battery indicates the number of minutes that power could be supplied in the event of a charging system failure, or a sizable current drain with the engine OFF . While there may be no guidelines regarding a minimum reserve capacity, the higher the capacity, the greater the "cushion".