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A car battery is a type of Rechargeable Battery that supplies electric energy to an Automobile . Usually this refers to a '''SLI battery''' (''Starting - Lighting - Ignition'') to power the Starter Motor , the lights and the Ignition System of a vehicle’s Engine . This also may describe a ''' Traction Battery ''' used for the main power source of an Electric Vehicle . Automotive starter batteries are usually Lead-acid Batteries that provide a nominal 12- Volt (actually 12.6 volts) Potential Difference by connecting in series six connecting six Cells that each produce about 2 to 2.1 volts. These batteries are made up of plates of Lead and Lead Oxide . These plates are submerged into a 35% Sulfuric Acid and 65% water solution called the Electrolyte solution. This process causes a Chemical Reaction that releases Electrons , allowing them to flow through conductors thus producing electricity. When a lead acid battery discharges, the materials of the lead plates react with the acid of the electrolyte, changing the surface of both plates to lead sulphate. When the battery is recharged, the chemical reaction is reversed. The lead sulphate reforms into lead oxide and lead, restoring the plates to their original condition, allowing the process to be repeated. TYPES Car batteries have different uses and various other elements are alloyed with the lead such as Calcium , Cadmium or Strontium to change Density , Hardness , or Porosity of the plates and to make the plates easier to manufacture.
Some batteries are claimed by their manufacturers to be dual purpose (starting and deep cycling). USE AND MAINTENANCE Fluid level Many automobile batteries have low maintenance requriements. If the battery has easily detachable caps then a top up may be required from time to time. Prolonged overcharging or charging at excessively high voltage causes some of the water in the electrolyte to be broken up into hydrogen and oxygen gases, which escape from the cells. If the liquid level drops too low, the plates are exposed to air, lose capacity and are damaged. In this case the caps are simply removed and the cells topped up with Distilled or Deionised Water just above the visible plates. Tap or rain water should never be used as they both can contain high levels of minerals which will impair battery performance. Charge and discharge In normal automotive service the vehicle's engine-driven Alternator powers the vehicle's electrical systems and restores charge used from the battery during engine cranking. When installing a new battery or recharging a battery that has been accidentally discharged completely, one of several different methods can be used to charge it. The most gentle of these is called Trickle Charging . Other methods include slow-charging and quick-charging, the latter being the harshest. In emergencies a battery can be Jump Started , by the battery of another vehicle or by a Hand Portable Battery Booster . Changing a battery In most modern automobiles, the Grounding is provided by connecting the body of the car to the negative electrode of the battery, a system called 'negative ground'. In the past this was different, some cars had 'positive ground', but such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge. Care should be taken when first filling the battery with Acid , as acids are highly corrosive and can damage human Skin and mucous membranes. When removing a car battery, the ground connection should be removed first and the other connection second. This ensures that a Short Circuit will not occur by a Wrench touching grounded engine parts while disconnecting the other terminal. When connecting a battery, connect the live connection first and then the grounded one. A 1994 study by the National Highway Traffic Safety Association estimated that in 1994 more than 2000 people were injured in the United States while working with automobile batteries. Freshness Because of " Sulfation " (see Lead-acid Battery ), one should never buy a battery that is more than six-months old. In the United States , the manufacturing date is printed on a sticker. The date can be written in plain text or using an alphanumerical code. The first character is a letter that specifies the month (A for January, B for February). The letter "I" is skipped due to its potential to be mistaken for the number 1. The second character is a single digit that indicates the year of manufacturing (for example, 6 for 2006). Corrosion Corrosion at battery terminals might prevent car from starting. Regularly clean terminals with wire brush and/or dissolve corrosion with mixed water and Baking Soda is needed. EXPLODING BATTERIES Maintenance free (MF) Batteries rely on valves fitted to each cell which can vent hydrogen if over-pressurisation occurs. Generally however, Oxygen and Hydrogen recombine in the space above the electrolyte, so that over-pressurisation rarely occurs. However, should such a condition occur, and the valves fail to operate (through being blocked for example), then there is a possibility of an internal Explosion if the oxy-hydrogen mixture is ignited. Just a slight jolt can cause a spark to jump between the posts, and the gas explodes. Personal injuries can result. The condition can be assessed if any swelling in the cell walls of the battery is visible. The swelling from internal pressurisation varies from cell to cell, that at the battery ends being most obvious, because the plastic is unsupported by cells at either side. It is surprising how powerful an explosion can be caused in the small air space above the electrolyte can occur, but when one cell explodes, it sets off a Chain Reaction in the rest. Such batteries should be isolated and discarded, taking great care using protective personal equipment (goggles, overalls, gloves etc) during the handling. TERMS AND RATINGS
Open circuit voltage is also affected by temperature, and the Specific Gravity of the electrolyte at full charge. Lead-acid The following is common for lead-acid batteries:
The energy to weight ratio, or specific energy, is in the range of 30 Wh/kg (108 kJ/kg). FORMATS
:The most commonly used battery for SLI applications. It has a low specific energy, but is cheaper than high-performance battery types.
:Used on some Battery Electric Car s. FUTURE TRENDS Due to the increase of electric power payloads in today’s automobile, a 42 V power system has been considered and is being developed to replace the existing 14 V power system. (14 V and 42 V refer to the alternator charging voltage). See for example Modeling of 36 V Lead Acid Battery for the 42 V Automotive System Simulation . For 42 V systems, 18 cell lead acid battery with a nominal 36 V is proposed. SEE ALSO REFERENCES EXTERNAL LINKS
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