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Group members. Priya jain(027) Shilpa mohanan (106) Suman sewani (095) Kruti shah (098) - Guided by prof. Krishna B. chauhan. B attery.
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Group members • Priya jain(027) • Shilpa mohanan (106) • Suman sewani (095) • Kruti shah (098) - Guided by prof. Krishna B. chauhan
Battery • Battery is a cell or connected group of cells that converts chemical energy into electrical energy by reversible chemical reactions and that may be recharged by passing a current through it in the direction opposite to that of its discharge -- called also storage cell. • A battery is also called an accumulator because it accumulates charge.
A real battery Battery Nomenclature 6v dry cell 9v battery Duracell batteries
Requirements of batteries • It should be capable of carrying large current at constant output power. • Its output voltage should remain constant for all the load currents. • Storage time should be as long as possible. • The battery should be compact and should occupy little space. • It should be cost effective. • It should be and maintenance free.
Battery symbol A battery converts chemical energy into electrical energy to produce emf between two electrodes.
Working of a battery • When in operation the electrochemical cell essentially discharges its chemical energy in favor of electric energy. • If the cell is connected via an external circuit from the cathode to the anode, electrons flow from the oxidized anode and are received by the cathode, which is subsequently reduced. • The electric circuit is completed by cations and anions, within the electrolyte, which flow to the cathode and anode, respectively. If the electrodes have emfs and , then the net emf is ; in other words, the net emf is the difference between the reduction potentials of the half-reactions. • The electrical driving force or across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts
The terminal voltage of a cell that is neither charging nor discharging is called the open-circuit voltage and equals the emf of the cell because of internal resistance , the terminal voltage of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit voltage. • An ideal cell has negligible internal resistance, so it would maintain a constant terminal voltage of until exhausted, then dropping to zero. • If such a cell maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it would perform 1.5 joules of work. • In actual cells, the internal resistance increases under the open circuit voltage also decreases under discharge. • If the voltage and resistance are plotted against time, the resulting graphs typically are a curve; the shape of the curve varies according to the chemistry and internal arrangement employed.
Types of Batteries • The primary batteryconverts chemical energy to electrical energydirectly, using the chemical materials within the cell to start the action. • The secondary battery must first be charged with electrical energy before it can convert chemical energy to electrical energy. • The secondary battery is frequently called a storage battery, since it stores the energy that is supplied to it.
Lead Acid Battery • Electrolyte for the most part distilled (pure) water, with some sulfuric acid mixed with the water. • Electrodes must be of dissimilar metals.
CONSTRUCTION OF LEAD ACID BATTERY • It is a collection of number of lead acid cells connected • in series with each other.
Current capacity and cell ratings. • The capacity of battery is expressed n ampere hour(AH). • It is defined as the product of a constant discharge current and the time duration beyond which the battery voltage falls below a voltage level called the “final discharge voltage”. • During the process of discharge the battery voltage should not be allowed fall below the “final discharge voltage” otherwise the battery life is shortened.
Factors affecting capacity of battery • The factors affecting the capacity of battery are: • Rate of discharge. • Temperature. • Density of electrolyte. • Area of plates. • The AH capacity decreases with increase in rate of discharge . As the rate of discharge increase ,the cell potential falls significantly ,due to internal losses. • The AH capacity increases with increase in temperature. • The density of the electrolyte decided the internal resistance . Hence with the increase in the electrolyte density, the battery capacity increases. • Capacity increases with increase in plate area.
Battery Efficiency • There are two different values of the cell efficiency: • Ampere-hour efficiency • Watt-hour efficiency. • AH efficiency: • The ampere-hour efficiency is defined as the ratio of ampere hours taken from the battery to the amperes hours supplied to it while charging. AH efficiency = A-H during discharge A-H input while charging
The typical value of AH efficiency is 90% to 95% .5% to 10% reduction is due to the losses taking place in the battery. • The ampere hour efficiency takes into account only the current and time but it does not consider the battery terminal voltage at all.
Watt-hour efficiency • The watt-hour efficiency is defined as follows: WH efficiency =AH efficiency * average cell voltage while discharging average cell voltage while charging • This equation can be modified and written as follows: • WH efficiency =Energy supplied by the battery while discharging. Energy supplied to the battery while charging. • The WH efficiency is less than AH efficiency . Typically it is 75% to 80%.
Battery lifetime • Primary batteries can loose 8 to 20% of their original charge every year. • This is known as the “ self discharge” • The rate of the side reactions is reduced if the batteries are stored at a low temperature , although some battries can be damaged by freezing. • High or low temperatures may reduce battery performance .this will affect the initial voltage or the battery. • For an AA alkaline battery this initial voltage is approximately normally distributed around 1.6volts.
Life of rechargeable batteries • Rechargeable batteries traditionally self discharge more rapidly than disposable alkaline batteries ; up to three percent a day • Due to their poor shelf life rechargeable batteries should not be stored and then relied upon to power flashlights or radios in an emergency. • NiCd batteries are almost “dead” when purchased ,and must be charged before first use. • Normally a fast charge ,rather than a slow overnight ,will result in a shorter battery lifespan • When a battery reaches the end of its lifetime ,it wii not suddenly lose all of its capacity , rather, its capacity will gradually decrease.
Extending battery • Battery life can be extending by storing the batteries at a low temperature ,as in a refrigerator freezer ,because the chemical reactions in the batteries are slower. • Such storage can extend the life of alkaline batteries by~5%,while the charge of rechargeable batteries can be extended from a few days upto several months. • In order to reach their maximum voltage , batteries must be returned to room temperature ,therefore ,alkaline battery manufactures like Duracell do not recommend refrigerating or freezing batteries.
Series connection of batteries • Positive terminal of one cell is connected to the negative terminal of the next, is called a series connected battery. • The voltage of this type of battery is the sum of a individual cell voltages.
Parallel connection of batteries • Connect the negative terminal from one cell to the negative of the next cell • Connect the positive terminal to the positive terminal, is parallel connected. • Voltage remains constant and the current is cumulative.
Dispose of alkaline batteries in the regular trash. • Alkaline, or manganese, batteries are used in flashlights, toys, remote controls and smoke alarms. • They range in size from AAA to 9 volts. In all state except California, which has strict disposal guidelines, alkaline batteries are considered standard municipal waste and can be thrown away normally. • You can also dispose of rechargeable alkaline or nickel metal hydride batteries in the regular trash. These types are safe for disposal in the normal municipal waste stream.
2. Dispose of carbon zinc batteries in the regular trash. Considered heavy-duty batteries, this type is made in all standard sizes and has a non-hazardous designation. Like alkaline batteries, they can be thrown in the trash.
3. Dispose of button batteries at a hazardous waste collection site. This kind of battery is used in hearing aids and watches and contains mercuric oxide, lithium, silver oxide or zinc-air. They are considered hazardous material and must be brought to a household hazardous waste collection site for proper handling.
4. Dispose of lithium and lithium-ion batteries at a battery recycling center. Lithium batteries are used in various small appliances and have been branded non-hazardous by the government. They are accepted at battery-recycling centers.
5. Dispose of rechargeable sealed lead-acid or nickel-cadmium batteries at a waste site. These types must be taken to either a household hazardous waste site, or they may also be taken to a recycling center
6. Dispose of lead-acid vehicle batteries at the retailer. Car batteries contain sulfuric acid and are either 6 or 12 volts. This type is large and contains very corrosive material. Most vehicle-battery retailers will dispose of your old battery when you buy a new one. Metal recyclers also will buy your old battery for scrap
MINIATURE BATTERY Energy: 100 mWh-2 Wh Applications : Electric watches, calculators, implanted medical devices (Mostly Primary Cells in small Button Cell packages)
Batteries for Portable Equipment Energy : 2 Wh-100 Wh Applications : Flashlights, toys, power tools, portable radio and TV, mobile phones, camcorders, lap-top computers, memory refreshing, instruments, cordless devices, wireless peripherals, emergency beacons .
Stationary Batteries Energy : 250 Wh-5 MWh Applications : Emergency power, local energy storage , remote relay stations, communication base stations, uninterruptible power supplies (UPS). (Mostly Lead Acid with Lithium recently making some inroads) SG ELECTRODE BATTERY
SG-ELECTRODE systems are based on our intelligent membrane electrode that enables the continuous in-situ measurement of specific gravity (SG) of electrolyte in flooded lead-acid battery cells. • In the past measuring SG has been a tedious operation usually performed manually with a hand-held suction-type hydrometer. • The SG-ELECTRODE provides a convenient and unique method of following battery charge and condition in a variety of situations, including traction batteries, stationary power supplies, backup batteries, submarine battery monitoring, etc.
