In science and technology, Battery is a device that stores chemical energy and makes it available in an electrical form.
Batteries are a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit. All batteries are made up of three basic components: an anode (the ‘-‘ side), a cathode (the ‘+’ side), and some kind of electrolyte (a substance that chemically reacts with the anode and cathode).
Types of Battery used in Substation
Lead Acid battery: used in vehicles, alarm systems and uninterrupted power supplies. the major advantage of this chemistry is its low cost.
Lithium Ion Battery: Used in Laptops, Modern camera phones, most other portable rechargeable digital equipment. This relatively modern battery type has a very high energy/mass.
Lithium ion polymer battery: similar characteristics to lithium-ion, but with slightly less energy/mass. This battery type can be shaped according to need,
Nickel cadmium battery: Used in many domestic applications but being superseded by Li-Ion and Ni-MH types.
Rating of Battery Cell
The electro chemical cells are rated in terms of voltage and ampere hour capacity. The ampere hour capacity represents the number of ampere hours that can be delivered under specified condition of temperature rate of discharge and the final voltage.
Ampere hours= Ampere X Hours. By series connection of n cells. Voltage will be nV and ampere hours AH.
Specific Gravity of electrolyte and Amount of Charge
Amount of Charge | 100% | 75% | 50% | 25% | 0% |
Specific Gravity | 1.28 | 1.24 | 1.20 | 1.16 | 1.12 |
Specific Gravity and voltage max. & min. limits
Parameter | Maximum | Minimum |
Voltage | 2.2 V | 1.8 V |
Specific Gravity | 1.28 | 1.18 |
Methods of charging of Battery
During the charging process, the current is forced into the battery from the opposite direction to its normal direction of current flow. In Normal ondition, Current leaves from positive terminal and enters through negative terminal. During Charging condition, Current enters through positive terminal and leaves from negative terminal.
Selecting of particular method depends on type of battery, charging facility available, service conditions, time available for charging, and the number of batteries to be charged at a given time.
Two methods are available for charging batteries
Quick charge method
In the quick charge method, the battery is given high charging current for a shorter duration of time. The current should never exceed half the ampere hour rating of the battery.This method generally not preferred.
Slow Charging method
The Thumb rule for deciding the rate of slow charging current is 10 % of AH. Thus proper charging rate for a 250 AH battery set would be 25 amperes. The source for charging a lead- acid battery should have a rated voltage of 2.5 V per cell- minimum.
The starting charging current is as above. The finishing charging current is very low of the order of 1 Amp. Before taking battery into service two charge discharge cycle must be taken. As the battery approaches full charge, it starts bubbling freely. The plastic caps on each cell should be kept loose.
The charging process is stopped after three successive hourly reading of hydrometer show no increase in the specific gravity. This charging method is preferred in substation.
Charging Batteries as per applied voltage and ampere
Constant voltage charging-Constant supply voltage approximately 2.63 volts-per-cell. Used for 8 hours charging.
Taper charging– Used only when identical batteries are to be charged. Voltage versus time characteristics and current versus time characteristics has dropping (taper) characteristics such that the initial voltage per cell is app. 2.2 V and final voltage per cell after 8 hours is app.2.0 V.
Two rates charging – Starting current for charging is set at higher value. -After certain time, current is changed to a lower value e.g. First four hours 2.4 V/Cell and 20 A next four hours 2.2 V/Cell and 5A.
Constant current charging -Generally not preferred, charging current should be controlled throughout the charging period by adjusting supply voltage.
Float charging method
In the float charging method, a constant voltage, set to a value just sufficient to finish the battery charge or to maintain the full charge is applied to the battery. Typical float charging voltage values range from about 2.15 V to 2.3 V per battery cell.
The float charging method is commonly used to maintain the charge of leadacid batteries used in stationary applications, such as in uninterruptable power supplies and SLI batteries (when the battery is charged from the motor alternator).
Trickle charging method
In the trickle charging method, a low-value constant current is applied to the battery. This small current is sufficient to maintain the full charge of a battery or to restore the charge of a battery that is used intermittently for short periods of time.
The trickle charging method, also called the compensating charge, is used to maintain the charge of batteries used for stationary applications and SLI batteries. During trickle charging, the battery is disconnected from the load.
Do’s and Don’t with Battery
Do’s
Read “Installation and operating manual” prior to installation of the batteries. Clean the batteries as and when dust accumulates. Battery room should have sufficient cooling. Re-torque the connections once every six months.
Keep the batteries away from heat source, sparks, fire etc. After a discharge recharge the battery immediately. Charge the batteries once every six months, if stored for long periods.
Don’t
Do not use metal funnel for topping distilled water or solution.Don’t overfill solution. Cables or bus bars should not touch the top surface of the battery. Don’t discharge excessive. Don’t allow leakage current. Don’t install physical damage cell. Don’t mix the batteries of different capacities and makes.
Common trouble and Solution for Batteries
Sr No | Common Trouble | Trouble Solution |
1 | Battery not taking charge | |
2 | Battery taking longer time | 1. Increase current setting and adopt higher |
3 | Overheating of battery | 1. Poor ventilation and charger giving out 2. Higher charging rate for too long period. 3. Ammeter reading low. Check ammeter. 4. Charged but specific gravity low and |
4 | Battery overheating while discharging | 1. High rate of discharge for longer time, reduce rate. 2. Separators between plates worn out. |
5 | Electrolyte level low | 1. Leaking of electrolyte through crack in jar, replace jar |
6 | Cell voltage unequal | 1. Over discharge, charge again 2.Level of electrolyte in some cells lower. |
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