Recombination Batteries

The recombination battery is one of the most recent advances in the automotive battery
FIGURE. The recombination battery is one of the most recent advances in the automotive battery. A recent variation of the automobile battery is the recombination battery. The recombination battery is sometimes called a gel-cell battery. It does not use a liquid electrolyte. Instead, it uses separators that hold a gel-type material. The separators are placed between the grids and have very low electrical resistance. The spiral design provides a larger plate surface area than that in conventional batteries. In addition, the close plate spacing results in decreased resistance. Because of this design, output voltage and current are higher than in conventional batteries. The extra amount of available voltage (approximately 0.6 V) assists in cold-weather starting. Also, gassing is virtually eliminated and the battery can recharge faster. FIGURE. Construction of the recombination battery cells. The following are some other safety features and advantages of the recombination battery: Contains no liquid electrolyte. If the case is cracked, no electrolyte will spill. Can be installed in any position, including upside down. Is corrosion free. Has very low maintenance because there is no electrolyte loss. Can last as much as four times longer than conventional batteries. Can withstand deep cycling without damage. Can be rated over 800 cold cranking amperes. Recombination batteries recombine the oxygen gas that is normally produced on the positive plates with the hydrogen given off by the negative plates. This recombination of oxygen and hydrogen produces water (H,0) and replaces the moisture in the battery. The electrolyte solution of the recombination battery is absorbed into the separators. The oxygen produced by the positive plates is trapped in the cell by special pressurized sealing vents. The oxygen gases then travel to the negative plates through small fissures in the gelled electrolyte. There are between one and six one-way safety valves in the top of the battery. The safety valves are necessary for maintaining a positive pressure inside of the battery case. This positive pressure prevents oxygen from the atmosphere from entering the battery and causing corrosion. Also, the safety valves must release excessive pressure that may be produced if the battery is overcharged. Absorbed Glass Mat Batteries A variation of the recombination battery is the absorbed glass mat (AGM) battery. Instead of using a gel, they hold their electrolyte in a moistened fiberglass matting. The matting is sandwiched between the battery's lead plates. The plates are made of high-purity lead and are tightly compressed into six cells. Separation...

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Hybrid Batteries

Hybrid grid and separator construction
Note: The following discussion on hybrid batteries refers to a battery type and not to the batteries that are used in hybrid electric vehicles (HEVs). The hybrid battery combines the advantages of the low-maintenance and maintenance-free battery. The hybrid battery can withstand six deep cycles and still retain 100% of its original reserve capacity. The grid construction of the hybrid battery consists of approximately 2.75% antimony alloy on the positive plates and a calcium alloy on the negative plates. This allows the battery to withstand deep cycling while retaining reserve capacity for improved cranking performance. Also, the use of antimony alloys reduces grid growth and corrosion. The lead calcium has less gassing than conventional batteries. FIGURE. Hybrid grid and separator construction. Grid construction differs from other batteries in that the plates have a lug located near the center of the grid. In addition, the vertical and horizontal grid bars are arranged in a radial pattern (Figure 5-15). By locating the lug near the center of the grid and using the radial grid design, the current has less resistance and a shorter path to follow to the lug. This means the battery is capable of providing more current at a faster rate. FIGURE. The hybrid battery grid construction allows for faster current delivery. Electrical energy at point "A" has a shorter distance to travel to get to the tab at point "B". The separators used are constructed of glass with a resin coating. The glass separators offer low electrical resistance with high resistance to chemical contamination. This type of construction provides for increased cranking performance and battery life.

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Maintenance-Free Batteries

Maintenance-free batteries
FIGURE. Maintenance-free batteries. In a ⚡ maintenance-free battery ⚡ there is no provision for the addition of water to the cells. The battery is sealed. It contains cell plates made of a slightly different compound than what is in a conventional battery. The plate grids contain calcium, cadmium, or strontium to reduce gassing and self-discharge. Gassing is the conversion of the battery water into hydrogen and oxygen gas. This process is also called electrolysis. The antimony used in conventional batteries is not used in maintenance-free batteries because it increases the breakdown of water into hydrogen and oxygen and because of its low resistance to overcharging. The use of calcium, cadmium, or strontium reduces the amount of vaporization that takes place during normal operation. The grid may be constructed with additional supports to increase its strength and to provide a shorter path, with less resistance, for the current to flow to the top tab. FIGURE. Maintenance-free battery grids with support bars give increased strength and faster electrical delivery. Each plate is wrapped and sealed on three sides by an envelope design separator. The envelope is made from microporous plastic. By enclosing the plate in an envelope, the plate is insulated and reduces the shedding of the active material from the plate. FIGURE. Construction of a maintenance-free battery. The battery is sealed except for a small vent so the electrolyte and vapors cannot escape. An expansion or condensation chamber allows the water to condense and drain back into the cells. Because the water cannot escape from the battery, it is not necessary to add water to the battery on a periodic basis. Containing the vapors also reduces the possibility of corrosion and discharge through the surface because of electrolyte on the surface of the battery. Vapors leave the case only when the pressure inside the battery is greater than atmospheric pressure. Note: If electrolyte and dirt are allowed to accumulate on the top of the battery case, it may create a conductive connection between the positive and negative terminals, resulting in a constant discharge on the battery. FIGURE. One cell of a maintenance-free battery has a built-in hydrometer, which gives indication of overall battery condition. Some maintenance-free batteries have a built-in hydrometer to indicate the state of charge. A hydrometer is a test instrument that is used to check the specific gravity of the electrolyte to determine the battery's state of charge. If the dot that is at the bottom...

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Chemical Action inside of the Battery

Chemical action that occurs inside of the battery during the discharge cycle
Activation of the battery is through the addition of electrolyte. This solution causes the chemical actions to take place between the lead peroxide of the positive plates and the sponge lead of the negative plates. The electrolyte is also the carrier that moves electric current between the positive and negative plates through the separators. The automotive battery has a fully charged specific gravity of 1.265 corrected to 80°F (27°C). Therefore, a specific gravity of 1.265 for electrolyte means it is 1.265 times heavier than an equal volume of water. As the battery discharges, the specific gravity of the electrolyte decreases because the electrolyte becomes more like water. The specific gravity of a battery can give you an indication of how charged a battery is. Fully charged: 1.265 specific gravity 75% charged: 1.225 specific gravity 50% charged: 1.190 specific gravity 25% charged: 1.155 specific gravity Discharged: 1.120 or lower specific gravity These specific gravity values may vary slightly according to the design of the battery. However, regardless of the design, the specific gravity of the electrolyte in all batteries will decrease as the battery discharges. Temperature of the electrolyte will also affect its specific gravity. All specific gravity specifications are based on a standard temperature of 80°F (27°C). When the temperature is above that standard, the specific gravity is lower. When the temperature is below that standard, the specific gravity increases. Therefore, all specific gravity measurements must be corrected for temperature. A general rule to follow is to add 0.004 for every 10°F (5.5°C) above 80°F (27°C) and subtract 0.004 for every 10°F (5.5°C) below 80°F (27°C). In operation, the battery is being partially discharged and then recharged. This represents an actual reversing of the chemical action that takes place within the battery. The constant cycling of the charge and discharge modes slowly wears away the active materials on the cell plates. This action eventually causes the battery plates to sulfate. The battery must be replaced once the sulfation of the plates has reached the point that there is insufficient active plate area. In the charged state, the positive plate material is essentially pure lead peroxide, PbO2. The active material of the negative plates is spongy lead, Pb. The electrolyte is a solution of sulfuric acid, H2SO4, and water. The voltage of the cell depends on the chemical difference between the active materials. FIGURE. Chemical action that occurs inside of the battery during the discharge cycle. The...

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Conventional Batteries

Conventional battery grid
The ⚡ conventional battery ⚡ is constructed of seven basic components: Positive plates. Negative plates. Separators. Case. Plate straps. Electrolyte. Terminals. The difference between "3-year" and "5-year" batteries is the quantity of material expanders used in the construction of the plates and the number of plates used to build a cell. Material expanders are fillers that can be used in place of the active materials. They are used to keep the manufacturing costs low. FIGURE. Conventional battery grid. A plate, either positive or negative, starts with a grid. Grids are generally made of lead alloys, usually antimony. About 5% to 6% antimony is added to increase the strength of the grid. The grid is the frame structure with connector tabs at the top. The grid has horizontal and vertical grid bars that intersect at right angles. An active material made from ground lead oxide, acid, and material expanders is pressed into the grid in paste form. The positive plate is given a "forming charge" that converts the lead oxide paste into lead peroxide. The negative plate is given a "forming charge" that converts the paste into sponge lead. FIGURE. A battery cell consists of alternate positive and negative plates. The negative and positive plates are arranged alternately in each cell element. Each cell element can consist of 9 to 13 plates. The positive and negative plates are insulated from each other by separators made of microporous materials. The construction of the element is completed when all of the positive plates are connected to each other and all of the negative plates are connected to each other. The connection of the plates is by plate straps. FIGURE. Construction of a battery element. A typical 12-volt automotive battery is made up of six cells connected in series. This means the positive side of a cell element is connected to the negative side of the next cell element. This is repeated throughout all six cells. By connecting the cells in series, the current capacity of the cell and cell voltage remain the same. The six cells produce 2.1 volts each. Wiring the cells in series produces the 12.6 volts required by the automotive electrical system. The plate straps provide a positive cell connection and a negative cell connection. The cell connection may be one of three types: through the partition, over the partition, or external. The cell elements are submerged in a cell case filled with electrolyte solution. Electrolyte consists...

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Automotive Batteries

Typical automotive 12-volt battery
An automotive battery is an electrochemical device capable of storing and producing electrical energy. Electrochemical refers to the chemical reaction of two dissimilar materials in a chemical solution that results in electrical current. When the battery is connected to an external load, such as a starter motor, an energy conversion occurs that results in an electrical current flowing through the circuit. Electrical energy is produced in the battery by the chemical reaction that occurs between two dissimilar plates that are immersed in an electrolyte solution. The automotive battery produces direct current (DC) electricity that flows in only one direction. When discharging the battery (current flowing from the battery), the battery changes chemical energy into electrical energy. It is through this change that the battery releases stored energy. During charging (current flowing through the battery from the charging system), electrical energy is converted into chemical energy. As a result, the battery can store energy until it is needed. FIGURE. Typical automotive 12-volt battery. The automotive battery has several important functions, including: It operates the starting motor, ignition system, electronic fuel injection, and other electrical devices for the engine during cranking and starting. It supplies all the electrical power for the vehicle accessories whenever the engine is not running or when the vehicle's charging system is not working. It furnishes current for a limited time whenever electrical demands exceed charging system output. It acts as a stabilizer of voltage for the entire automotive electrical system. It stores energy for extended periods of time. NOTE! The battery does not store energy in electrical form. The battery stores energy in chemical form. The largest demand placed on the battery occurs when it must supply current to operate the starter motor. The amperage requirements of a starter motor may be over several hundred amperes. This requirement is also affected by temperatures, engine size, and engine condition. After the engine is started, the vehicle's charging system works to recharge the battery and to provide the current to run the electrical systems. Most AC generators have a maximum output of 60 to 150 amperes. This is usually enough to operate all of the vehicle's electrical systems and meet the demands of these systems. However, under some conditions (such as the engine running at idle) generator output is below its maximum rating. If there are enough electrical accessories turned on during this time (heater, wipers, headlights, and radio) the demand may exceed the AC...

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