Warning: Refer to Batteries Produce Explosive Gases Warning in the Preface section.
The battery has three major functions in the electrical system. First, the battery provides a source of energy for cranking the engine. Second, the battery acts as a voltage stabilizer for the electrical system. Finally, the battery can, for a limited
time, provide energy when the electrical demand exceeds the output of the generator.
The sealed battery is standard on all cars. There are no vent plugs in the cover. The battery is completely sealed, except for 2 small vent holes in the sides. These vent holes allow the small amount of gas produced in the battery to escape.
The sealed battery has the following advantages over conventional batteries:
| • | No water need be added for the life of the battery. |
| • | It is protected against overcharge. If too much voltage is applied to the battery, it will not accept as much current as a conventional battery. In a conventional battery, the excess voltage will still try to charge the battery, leading to gassing,
which causes liquid loss. |
| • | It is not as liable to self-discharge as a conventional battery. This is particularly important when a battery is left standing for long periods of time. |
| • | It has more power available in a lighter and a smaller case. |
Ratings
A battery has 2 ratings:
- A reserve capacity rating designated at 27°C (80°F), which is the time a fully charged battery will provide 25 amperes current flow at or above 10.5 volts
- A cold cranking amp rating determined under testing at -18°C (0°F), which indicates the cranking load capacity.
Reserve Capacity
The reserve capacity is the maximum length of time it is possible to travel at night with the minimum electrical load and no generator output. Expressed in minutes, Reserve Capacity (or RC rating) is the time required for a fully charged battery, at a
temperature of 27°C (81°F) and being discharged at a current of 25 amperes, to reach a terminal voltage of 10.5 volts.
Cold Cranking Amperage
The cold cranking amperage test is expressed at a battery temperature of -18°C (0°F). The current rating is the minimum amperage, which must be maintained by the battery for 30 seconds at the specified temperature, while meeting a
minimum voltage requirement of 7.2 volts. This rating is a measure of cold cranking capacity.
The battery is not designed to last indefinitely. However, with proper care, the battery will provide many years of service.
If the battery tests well, but fails to perform satisfactorily in service for no apparent reason, the following factors may point to the cause of the trouble:
| • | Vehicle accessories are left on overnight. |
| • | Slow average driving speeds are used for short periods. |
| • | The vehicle electrical load is more than the generator output, particularly with the addition of aftermarket equipment. |
| • | There are defects in the charging system, such as electrical shorts, a slipping generator belt, a faulty generator, or a faulty voltage regulator. |
| • | There has been battery abuse, including failure to keep the battery cable terminals clean and tight, or a loose battery hold-down. |
| • | There are mechanical problems in the electrical system, such as shorted or pinched wires. |
Built-In Hydrometer
The sealed battery has a built-in, temperature-compensated hydrometer in the top of the battery. This hydrometer is to be used with the following diagnostic procedure:
- When observing the hydrometer, make sure that the battery has a clean top.
- Under normal operation, 2 indications can be observed:
| • | GREEN DOT VISIBLE--Any green appearance is interpreted as a green dot, meaning the battery is ready for testing. |
| • | DARK GREEN DOT IS NOT VISIBLE--If there is a cranking complaint, the battery should be tested. The charging and electrical systems should also be checked at this time. |
- Occasionally, a third condition may appear:
CLEAR OR BRIGHT YELLOW--This means the fluid level is below the bottom of the hydrometer. This may have been caused by excessive or prolonged charging, a broken case, excessive tipping,
or normal battery wear. Finding a battery in this condition may indicate high charging by a faulty charging system. Therefore, the charging and the electrical systems may need to be checked if a cranking complaint exists. If the cranking complaint is caused
by the battery, replace the battery.
