See Figure 1
Check the battery fluid level (except in maintenance-free batteries) in each cell at least once a month, more often during extreme weather (mid-summer and mid-winter) and extended periods of travel. The electrolyte (water) level should be about 3 / 8 in. (9.5mm) above the plates as you look down into each cell. Filling each cell to the bottom of the cell ring is satisfactory.
Some battery makes are equipped with an eye in the cap of one cell. If this eye glows or has an amber color to it, this means that the level is low and only distilled water should be added. If the eye has a dark appearance the battery electrolyte level is high enough. It is also wise to check each cell individually on these eye type batteries.
Distilled water is the only fluid you should add to your car's battery. It is widely available in supermarkets and auto stores. Tap water in most areas of the U.S. contains chemicals and minerals that are harmful in the long run to battery plates.
When adding water to a battery in freezing weather, the car should be driven immediately for a few miles so that the water and electrolyte mix. Otherwise, the battery may freeze.
The specific gravity of the battery should be checked at every tune-up, as outlined later in this section. If the battery terminals become corroded, they must be cleaned using a wire brush or battery cleaning tool. Clamps and terminals should be shiny for a good connection and the clamps should be coated lightly with petroleum jelly when assembled to the terminal posts, to retard corrosion.
A trickle charger (slow charger) is recommended for battery charging. If a fast charger must be used while the battery is in the car, disconnect the battery before connecting the charger.
TESTING THE MAINTENANCE-FREE BATTERY
See Figure 2
All later model cars are equipped with 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.
The sealed-top battery cannot be checked for charge in the normal manner, since there is no provision for access to the electrolyte. To check the condition of the battery:
- If the indicator eye on top of the battery is dark, the battery has enough fluid. If the eye is light, the electrolyte fluid is too low and the battery must be replaced.
- If a green dot appears in the middle of the eye, the battery is sufficiently charged. Proceed to Step 4. If no green dot is visible, charge the battery.
- Charge the battery.
It may be necessary to tip the battery from side to side to get the green dot to appear after charging.
- 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 appropriate test load.
Apply the load for 15 seconds while reading the voltage. Disconnect the load.
- Check the results. If the battery voltage is at or above the specified voltage (9.6 volts), the battery is good.
If the voltage falls, the battery should be replaced.
SPECIFIC GRAVITY CHECK EXCEPT MAINTENANCE FREE BATTERIES
See Figure 3
Check the specific gravity of the battery (your diesel has two) at every tune-up for gasoline engines and at every oil change for diesels. It should be between 1.20-1.30 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 acid) into the hydrometer to just lift the float. The specific gravity is then read to 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, it is a big difference between two or more cells that should be of concern. Generally, if after charging, the specific gravity between any two cells varies more than 50 points (.050), 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 must be relied on to display any signs of battery deterioration. If the indicator is dark, the battery can be assumed to be OK. If the indicator is light, the specific gravity is low and the battery should be charged or replaced.
CABLES AND CLAMPS
See Figures 4, 5, 6, 7, 8 and 9
Twice a year, the battery terminal posts and the cable clamps should be cleaned. Loosen the clamp bolts (you may have to brush off any corrosion with a baking soda and water solution if they are really messy) and remove the cables, negative cable first. On batteries with posts on top, the use of a battery clamp puller is recommended-it is easy to break off a battery terminal if a clamp gets stuck without the puller. These pullers are inexpensive and available in most auto parts stores or auto departments. Side terminal battery cables are secured with a bolt.
The best tool for battery clamp and terminal maintenance is a battery terminal brush. This inexpensive tool has a female-ended wire brush for cleaning terminals, and a male-ended wire brush inside for cleaning the insides of battery clamps. When using this tool, make sure you get both the terminal posts and the insides of the clamps nice and shiny-any oxidation, corrosion or foreign material will prevent a sound electrical connection and inhibit either starting or charging. If your battery has side terminals, there is also a cleaning tool available for these.
Before installing the cables, remove the battery hold-down clamp or strap and remove the battery. Inspect the battery casing for leaks or cracks (which unfortunately can only be fixed by buying a new battery). Check the battery tray, wash it off with warm soapy water, rinse and dry. Any rust on the tray should be sanded away, and the tray given at least two coats of a quality anti-rust paint. Replace the battery, and install the hold-down clamp or strap, but do not overtighten.
Reinstall your clean battery cables, negative cable last. Tighten the cables on the terminal posts snugly; do not overtighten. Wipe a thin coat of petroleum jelly or grease all over the outside of the clamps. This will help to inhibit corrosion.
Finally, check the battery cables themselves. If the insulation of the cables is cracked or broken, or if the ends are frayed, replace the cable with a new cable of the same length or gauge.
BATTERY CHARGING AND REPLACEMENT
Charging a battery is best done by the slow-charging method (often called trickle charging), with a low-amperage charger. Quick charging a battery can actually cook the battery, damaging the plates inside and decreasing the life of the battery drastically. Any charging should be done in a well-ventilated area away from the possibility of sparks or flame. The cell caps (not found on maintenance-free batteries) should be unscrewed from their cells, but not removed.
If the battery must be quick charged, check the cell voltages and the color of the electrolyte a few minutes after the charge is started. If cell voltages are not uniform or if the electrolyte is discolored with brown sediment, stop the quick charging in favor of a trickle charge. A common indicator of an overcharged battery is the frequent need to add water to the battery.