In today’s world, life without electricity is unimaginable. From a small light bulb to large motors and for many other major purposes, electrical energy is the main source. As the importance of electricity in everyone’s life is increasing, it is in other way increasing the demand. As of 2016 May, 303 kW is the installed capacity of utility sector in India. There is a shortage of 2.1% of total electricity in India. All this demand cannot be met alone by installing more generation. By reducing consumption, by reducing losses or by increasing private participation in energy generation, load on the utility can be decreased. By using regeneration, usage of renewable energy sources in the form of private power generation, co generation etc., power demand can be reduced. There is a scope for reduction of losses in many sectors, which use bulk electric supply. One such application of electric power is for batteries.
In railways, batteries play a vital role. The battery used in railways is lead acid battery, which is the most popular rechargeable battery worldwide. Both the battery product and manufacture process are proven economical and reliable. These are specially designed for railway application to withstand deep cycling.
Railway batteries are typically used for rolling stock or stationary applications. Rolling stock batteries are used for locomotive starting, lighting, on board auxiliary system in engines and coaches. Stationary batteries are used as emergency backup power for railroad crossings, signal towers and signaling systems. Batteries are also used to provide illumination, fan, air conditioning, and other miscellaneous needs of electricity for travelling passengers. Hence, battery capacity, robustness, reliability and performance are important for their effective utilization. The batteries are received at railway workshop once in eighteen months to ensure the above said features. These features are ensured by conducting various tests. Discharge process which is one of the performance tests conducted on batteries to check its capacity and reliability.
In discharge test the batteries are charged and discharged for 3 cycles. Lead Acid battery uses constant current, constant voltage charge method. A regulated current raises the terminal voltage until the upper voltage limit is reached at which point current drops due to saturation. It is charged in three stages:
1. Constant current charge
2. Topping charge
3. Float charge
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