Battery: Description and Operation
BATTERYMaintenance-Free Battery - Typical:
A large capacity, maintenance-free storage battery is standard factory-installed equipment on this model. Male post type terminals made of a soft lead material protrude from the top of the molded plastic battery case to provide the means for connecting the battery to the vehicle electrical system. The battery positive terminal post is visibly larger in diameter than the negative terminal post, for easy identification. The letters POS and NEG are also molded into the top of the battery case adjacent to their respective positive and negative terminal posts for additional identification confirmation. Refer to Battery Cables for more information on the battery cables that connect the battery to the vehicle electrical system.
This battery is designed to provide a safe, efficient and reliable means of storing electrical energy in a chemical form. This means of energy storage allows the battery to produce the electrical energy required to operate the engine starting system, as well as to operate many of the other vehicle accessory systems for limited durations while the engine and/or the charging system are not operating. The battery is made up of six individual cells that are connected in series. Each cell contains positively charged plate groups that are connected with lead straps to the positive terminal post, and negatively charged plate groups that are connected with lead straps to the negative terminal post. Each plate consists of a stiff mesh framework or grid coated with lead dioxide (positive plate) or sponge lead (negative plate). Insulators or plate separators made of a non-conductive material are inserted between the positive and negative plates to prevent them from contacting or shorting against one another. These dissimilar metal plates are submerged in a sulfuric acid and water solution called an electrolyte.
The factory-installed battery has a built-in test indicator (hydrometer). The color visible in the sight glass of the indicator will reveal the battery condition. For more information on the use of the built-in test indicator, refer to Battery diagnosis and testing procedures. The factory-installed maintenance-free battery has non-removable battery vent caps. Water cannot be added to this battery. The chemical composition of the metal coated plates within the maintenance-free battery reduces battery gassing and water loss, at normal charge and discharge rates. Therefore, the battery should not require additional water in normal service. If the electrolyte level in this battery does become low, the battery must be replaced. However, rapid loss of electrolyte can be caused by an over-charging condition. Be certain to diagnose the charging system after replacing the battery for a low electrolyte condition and before returning the vehicle to service. Refer to Charging System diagnosis and testing procedures.
For battery maintenance schedules and jump starting procedures, see the owner's in the vehicle glove box. While battery charging can be considered a maintenance procedure, the battery charging procedures and information are located in the service procedures of this service. This was done because the battery must be fully-charged before any battery diagnosis or testing procedures can be performed. Refer to Battery Charging procedures.
BATTERY SIZE AND RATINGS
The battery Group Size number, the Cold Cranking Amperage (CCA) rating, and the Reserve Capacity (RC) rating or Ampere-Hours (AH) rating can be found on the original equipment battery label. Be certain that a replacement battery has the correct Group Size number, as well as CCA, and RC or AH ratings that equal or exceed the original equipment specification for the vehicle being serviced. Refer to Battery specifications. Battery sizes and ratings are discussed in more detail below.
- Group Size
The outside dimensions and terminal placement of the battery conform to standards established by the Battery Council International (BCI). Each battery is assigned a BCI Group Size number to help identify a correctly-sized replacement.
- Cold Cranking Amperage
The Cold Cranking Amperage (CCA) rating specifies how much current (in amperes) the battery can deliver for thirty seconds at -180 °C (0 °F). Terminal voltage must not fall below 7.2 volts during or after the thirty second discharge period. The CCA required is generally higher as engine displacement increases, depending also upon the starter current draw requirements.
- Reserve Capacity
The Reserve Capacity (RC) rating specifies the time (in minutes) it takes for battery terminal voltage to fall below 10.5 volts, at a discharge rate of 25 amperes. RC is determined with the battery fully- charged at 26.7 °C (80 °F). This rating estimates how long the battery might last after a charging system failure, under minimum electrical load.
- Ampere-Hours
The Ampere-Hours (AH) rating specifies the current (in amperes) that a battery can deliver steadily for twenty hours, with the voltage in the battery not falling below 10.5 volts. This rating is also sometimes identified as the twenty-hour discharge rating.
When an electrical load is applied to the terminals of the battery, an electrochemical reaction occurs. This reaction causes the battery to discharge electrical current from its terminals. As the battery discharges, a gradual chemical change takes place within each cell. The sulfuric acid in the electrolyte combines with the plate materials, causing both plates to slowly change to lead sulfate. At the same time, oxygen from the positive plate material combines with hydrogen from the sulfuric acid, causing the electrolyte to become mainly water. The chemical changes within the battery are caused by the movement of excess or free electrons between the positive and negative plate groups. This movement of electrons produces a flow of electrical current through the load device attached to the battery terminals.
As the plate materials become more similar chemically, and the electrolyte becomes less acid, the voltage potential of each cell is reduced. However, by charging the battery with a voltage higher than that of the battery itself, the battery discharging process is reversed. Charging the battery gradually changes the sulfated lead plates back into sponge lead and lead dioxide, and the water back into sulfuric acid. This action restores the difference in the electron charges deposited on the plates, and the voltage potential of the battery cells. For a battery to remain useful, it must be able to produce high-amperage current over an extended period. A battery must also be able to accept a charge, so that its voltage potential may be restored.
The battery is vented to release excess hydrogen gas that is created when the battery is being charged or discharged. However, even with these vents, hydrogen gas can collect in or around the battery. If hydrogen gas is exposed to flame or sparks, it may ignite. If the electrolyte level is low, the battery may arc internally and explode. If the battery is equipped with removable cell caps, add distilled water whenever the electrolyte level is below the top of the plates. If the battery cell caps cannot be removed, the battery must be replaced if the electrolyte level becomes low.
In addition to producing and storing electrical energy; the battery serves as a capacitor and voltage stabilizer for the electrical system of the vehicle. It absorbs most abnormal or transient voltages caused by the switching of any of the electrical components in the vehicle.
Battery Cables - Typical:
BATTERY CABLES
The battery cables are large gauge, stranded copper wires sheathed within a heavy plastic or synthetic rubber insulating jacket. The wire used in the battery cables combines excellent flexibility and reliability with high electrical current carrying capacity.
The battery cables cannot be repaired and, if damaged or faulty they must be replaced. Both the battery positive and negative cables are available for service replacement only as a unit with the battery positive cable wire harness or the battery negative cable wire harness, which may include portions of the wiring circuits for the generator and other components on some models.
Gasoline engine models feature a stamped brass clamping type female battery terminal crimped onto one end of the battery cable wire and then solder-dipped. A square headed pinch-bolt and hex nut are installed at the open end of the female battery terminal clamp. The battery positive cable also includes a red molded rubber protective cover for the female battery terminal clamp. Large eyelet type terminals are crimped onto the opposite end of the battery cable wire and then solder-dipped. The battery positive cable wires have a red insulating jacket to provide visual identification and feature a larger female battery terminal clamp to allow connection to the larger battery positive terminal post. The battery negative cable wires have a black insulating jacket and a smaller female battery terminal clamp.
The battery positive cable terminal clamp is crimped onto the ends of two wires. One wire has an eyelet terminal that connects the battery positive cable to the B(+) terminal stud of the Power Distribution Center (PDC), and the other wire has an eyelet terminal that connects the battery positive cable to the B(+) terminal stud of the engine starter motor solenoid. The battery negative cable terminal clamp is also crimped onto the ends of two wires. One wire has an eyelet terminal that connects the battery negative cable to the vehicle powertrain through a stud on the front of the left engine cylinder head. The other wire has an eyelet terminal that connects the battery negative cable to the vehicle body through a ground screw on the left front fender inner shield, just ahead of the battery. An additional ground wire with two eyelet terminals is used to provide ground to the vehicle frame. One eyelet terminal of this ground wire is installed under the head of the battery negative cable terminal clamp pinch-bolt, and the other eyelet terminal is secured with a ground screw to the outer surface of the left frame rail, below the battery.
Battery Hold Downs - Typical:
BATTERY HOLD DOWNS
The battery hold down hardware includes two bolts, two U-nuts and a hold down strap. The battery hold down bracket consists of a formed steel rod with a stamped steel angle bracket welded to each end. The hold down bracket assembly is then plastic-coated for corrosion protection. Models equipped with the optional diesel engine have a second battery installed in a second battery tray on the right side of the engine compartment. The hold down hardware for the right side battery is mirror image of the hold down hardware used for the left side battery.
When installing a battery into the battery tray, be certain that the hold down hardware is properly installed and that the fasteners are tightened to the proper specifications. Improper hold down fastener tightness, whether too loose or too tight, can result in damage to the battery, the vehicle or both. Refer to Battery Hold Downs installation procedures, including the proper hold down fastener tightness specifications.
The battery hold down hardware secures the battery to the battery tray in the engine compartment. This hardware is designed to prevent battery movement during vehicle operation. Unrestrained battery movement during vehicle operation can result in damage to the vehicle, the battery or both.
The two hold down U-nuts are installed onto the battery tray before the tray is installed in the engine compartment. The U-nuts are installed over a hole in a molded formation integral to each side of the battery tray. After the battery is properly positioned in the battery tray, the battery hold down strap is installed across the top of the battery case. A long hold down bolt is then installed through a hole in the angle bracket on each end of the battery hold down strap and threaded into the U-nuts on the battery tray. The hold down bolts are then tightened to securely hold down the battery in the battery tray.
Battery Tray - Typical:
BATTERY TRAY
The battery is mounted in a molded plastic tray with an integral support located in the left front corner of the engine compartment. A U-nut held in a molded formation on each side of the battery tray provides anchor points for the battery hold down bolts. The battery tray is secured on the outboard side to the inner fender shield by two hex screws with washers, and from underneath the integral battery tray support is secured to the left front wheelhouse inner panel by two stud plates. Each stud plate has two studs and is secured by two nuts with washers. The stud plate that secures the front of the battery tray support to the wheelhouse inner panel is installed through the wheelhouse panel from the top. The stud plate that secures the rear of the battery tray support to the wheelhouse inner panel is installed through the wheelhouse panel from the bottom.
A hole in the bottom of the battery tray is fitted with a battery temperature sensor. Refer to Battery Temperature Sensor. Models that are equipped with an optional vehicle speed control system have the speed control servo secured to the integral battery tray support. Refer to Speed Control Servo.
Models that are equipped with the diesel engine option have a second battery tray located in the right front corner of the engine compartment. This second battery tray and its mounting are mirror image of the standard equipment left battery tray. However, the right battery tray and support have no provisions for a battery temperature sensor or a speed control servo mounting bracket.
The battery tray provides a mounting location and support for the vehicle battery. The battery tray also provides anchor points for the battery hold down hardware. The battery tray and the battery hold down hardware combine to secure and stabilize the battery in the engine compartment, which prevents battery movement during vehicle operation. Unrestrained battery movement during vehicle operation can result in damage to the vehicle, the battery or both.