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, making it discharge more quickly and the corrosive acid can eat away at 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, usually by the color of the "eye". If this type of battery is too low on electrolyte, it must be replaced.
FLUID LEVEL (EXCEPT MAINTENANCE FREE BATTERIES)
Check the battery electrolyte level at least once a month, or more often in hot weather or during periods of extended operation. The level can be checked through the case on translucent polypropylene batteries; the cell caps must be removed on other models. The electrolyte level in each cell should be kept filled to the split ring inside, or the line marked on the outside of the case.
If the level is low, add only distilled water, or colorless, odorless drinking water, through the opening until the level is correct. Each cell is completely separate from the others, so each must be checked and filled individually.
If water is added in freezing weather, the car should be driven several miles to allow the water to mix with the electrolyte. Otherwise, the battery could freeze.
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 auto parts stores. Side terminal battery cables are secured with a special 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.
A true test of a battery's condition is the load test. It requires the use of a special carbon pile to simulate an electrical load on the battery. Normally a battery is load tested at half its cold cranking amps rating or at 3 times the amp-hour rating for 15 seconds. Generally, if after 15 seconds the battery voltage is not at 9.6 volts or more, the battery either needs to be charged or replaced.
Specific Gravity (Except Maintenance-Free Batteries)
At least once a year, check the specific gravity of the battery. It should be between 1.25 in. Hg and 1.27 in. Hg at room temperature.
The specific gravity can be checked with the use of a hydrometer, an inexpensive tool available from auto parts stores. The hydrometer has a squeeze bulb at one end and a nozzle at the other. Battery electrolyte is sucked into the hydrometer until the float is lifted from its seat. The specific gravity is then read by noting the position of the float. Generally, if after charging, the specific gravity between any two cells varies more than 50 points (0.50), the battery is bad and should be replaced.
It is not possible to check the specific gravity in this manner on sealed (maintenance-free) batteries. Instead, the indicator built into the top of the case is used to display the condition of the battery's charge and also the level of electrolyte.
Generally, a battery should be charged at a slow rate to keep the plates inside from getting too hot. This would shorten the life of the battery. However, if some maintenance-free 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.
When it becomes necessary to replace the battery, be sure to select a new battery with a cold cranking amp rating equal to or greater than the battery originally installed. Deterioration of connections, starter condition and alternator condition make the battery's job all the more difficult as time goes on. The tendency for increasing 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 .