All batteries, regardless of type, should be kept clean on the outside and should be kept tightly secured by a battery hold-down device. If this is not done, battery acid can leak out, shortening the life of the battery, make it discharge more quickly and the corrosive acid can eat away components under the hood. A battery that is not a maintenance-free type must be checked periodically for water level. A maintenance-free type battery cannot have water added to it, but it must also be checked for electrolyte level. This can be done by looking at the color of the "eye". If this battery is too low on electrolyte, it must be replaced.
Except Maintenance-Free Batteries
Fill each cell to about 3 / 8 in. (9.5mm) above the tops of the plates. Always use distilled water (available in supermarkets or auto parts stores). Most tap water contains chemicals and minerals that may slowly damage the plates of your battery.Maintenance-Free Batteries
Some later model cars are equipped with sealed maintenance-free batteries which do not require normal attention as far as fluid level checks are concerned. However, the terminals require periodic cleaning which should be performed at least once a year.
CABLES AND CLAMPS
Once a year, the battery terminals and the cable clamps should be cleaned. Loosen the clamps and remove the cables, negative cable first. On batteries with posts on top, the use of a puller specially made for the purpose is recommended. These are inexpensive, and available in most auto parts stores. Side terminal battery cables are secured with a bolt.
Clean the cable clamps and the battery terminal with a wire brush, until all corrosion, grease, etc. is removed and the metal is shiny. It is especially important to clean the inside of the clamp thoroughly, since a small deposit of foreign material or oxidation there will prevent a sound electrical connection and inhibit either starting or charging. Special tools are available for cleaning these parts, one type for conventional batteries and another type for side terminal batteries.
Before installing 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, but be careful not to overtighten, which will crack the battery case.
After the clamps and terminals are clean, reinstall the cables, negative cable last. Do not hammer on the clamps to install. Tighten the clamps securely, but do not distort them. Give the clamps and terminals a thin external coat of grease after installation, to retard corrosion.
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.
Check the specific gravity of the battery at every tune-up. It should be between 1.20 and 1.30 at room temperature. The specific gravity is checked with a hydrometer, an inexpensive instrument available in most auto parts stores, auto departments and many hardware stores. The hydrometer looks like a turkey baster, having a rubber squeeze bulb on one end and a nozzle at the other. Insert the nozzle end into each battery cell and suck enough electrolyte (battery water) into the hydrometer to just lift the float. The specific gravity is then read by the graduations on the float. Some hydrometers are color coded, with each color signifying a certain range of specific gravity.
All cells of your battery should produce nearly equal specific gravity readings. Do not be extremely alarmed if all of your battery's cells are equally low (but check to see if your alternator belt is tight); however, a big difference between two or more cells should be a concern. Generally, if after charging, the specific gravity between any two cells varies more than 50 points (0.050), the battery is bad and should be replaced.
Batteries should be checked for proper electrolyte level at least once a month or more frequently. Keep a close eye on any cell or cells that are unusually low or seem to constantly need water. This may indicate a battery on its last legs, a leak, or a problem with the charging system.
The maintenance-free battery cannot be checked for charge by checking the specific gravity using a hand-held hydrometer. Instead, the built-in hydrometer must be used in order to determine the current state of charge. Check your owners manual or with your local car dealer for the proper color of the "eye" on your battery. Most (not all) built in hydrometers are a green color when the battery is charging properly. If you are unable to see the hydrometer color make sure that the "eye" is clean by wiping it with a paper towel or clean rag. If you are still unable to read the hydrometer gently shake the battery. If the eye on top of the battery is green, the battery electrolyte level is all right. If the eye is dark, the electrolyte level is too low and the battery must be replaced.Load Testing
- Connect a battery load tester and a voltmeter across the battery terminals (the battery cables should be disconnected from the battery). Apply a 300 amp load to the battery for 15 seconds to remove the surface charge. Remove the load.
- Wait 15 seconds to allow the battery to recover.
- Apply the appropriate test load for 15 seconds, while reading the voltage. Disconnect the load.
- Check the results against the appropriate chart. If the battery voltage was at or above the specified voltage for the temperature listed, the battery is good. If the voltage falls below what's listed, the battery should be replaced.
Generally, a battery should be charged at a slow rate to keep the plates inside from getting too hot. However, if some batteries are allowed to discharge until they are almost "dead", they may have to be charged at a high rate to bring them back to life. On maintenance-free batteries it may be necessary to tip the battery from side to side to get the built in hydrometer "eye" to register it's green color after charging.
Charge the battery at the proper charging rate (amps) and time span.
When it becomes necessary to replace the battery, select a battery with a rating equal to or greater than the battery originally installed. Deterioration, embrittlement and just plain aging of the battery cables, starter motor, and associated wires makes the battery's job harder in successive years. The slow increase in electrical resistance over time makes it prudent to install a new battery with a greater capacity than the old. Details on battery removal and installation are covered in .
- Carefully disconnect the negative cable from the battery terminal.
- With the negative battery cable disconnected and out of the way, carefully disconnect the positive cable from the battery terminal.
- Loosen the nut and/or bolt retaining the battery strap or clamp. Remove the battery retainer.
- Wearing an old pair of work gloves or using a battery lifting tool, carefully lift the battery out of the vehicle and place it in a safe location. Be sure to keep the battery away from an open flame.
- Inspect the battery tray and cables for damage and corrosion. As necessary, clean or repair the tray and cables.
- Carefully lower the battery and position it in the tray, making sure not to allow the terminals to short on any bare metal during installation.
- Position and secure the battery retainer strap or clamp.
- Connect the positive cable to the positive battery terminal.
- Connect the negative cable to the negative battery terminal.