Why AC Supply is Not Used in a Battery
Understanding the unique properties of batteries and the differences between AC and DC supply can help clarify why AC supply is not typically used in batteries. In this article, we will explore the underlying principles and methodology, examining the suitability and practicality of AC supply for battery operations.
Chemical Reactions and Direct Current (DC) Supply
Batteries release energy through a chemical reaction. This reaction, like a waterfall, flows in one direction, converting chemical energy into electrical energy. Essentially, batteries burn zinc directly into electricity, a process that is unidirectional and does not oscillate.
In contrast, AC supply is a result of rotating motion, producing a sine wave. This natural oscillation corresponds to the alternating current produced by alternators, which rely on rotating magnetic fields to induce currents.
Batteries supply DC voltage because the chemical reactions responsible for their operation are inherently unidirectional. The electrochemical process that powers batteries only works in one direction.
No AC Batteries Exist
It's important to note that there are no batteries that function on AC supply. Stored DC voltage can be converted to AC using inverters, but these are not integrated into the battery itself.
Why Batteries Supply DC Voltage
Batteries are fundamentally a chemical storage of electrical energy. The electrochemical reaction that occurs within batteries involves an anode, electrolyte, and a cathode, all of which have a certain electro-potential. This electro-potential is always DC and does not reverse periodically.
Batteries can technically be used to run AC systems, but the size and cost would be enormous, and AC is typically provided by the grid supply. The grid provides the necessary voltage and frequency to maintain a stable AC current.
The Impracticality of AC in Batteries
The electrochemical reaction within a battery must flow in one direction. Alternating current, or AC, flows in both directions, which makes it unsuitable for charging a battery. The polarity of charging terminals in AC changes with the frequency of the supply, causing the battery to charge and discharge cyclically. This results in an alternating charge and discharge process, which is not optimal for battery long-term performance.
To charge a battery using AC, the current must be converted to DC. The most common method is to use diodes, which allow current to flow in only one direction. By ensuring that current flows only one way, the battery can be fully charged without discharging in the next half cycle.
As an analogy, consider a bucket (battery) being filled with water (electrons). If we were to pour water (AC current) into the bucket and then immediately take it out again, the bucket would never fill up. To fill the bucket, we must ensure the water (current) flows continuously in one direction. If we applied AC directly to the battery, we would be charging in one half cycle and discharging in the next, resulting in zero net charge gain.
In practice, applying AC to a battery will quickly reduce its lifespan due to the cyclic stress on the chemical components. Continuous charging and discharging can lead to degradation and eventual failure of the battery.
Ultimately, the use of DC supply for battery charging is more efficient and long-lasting. Converting AC to DC for charging purposes is a standard practice that ensures optimal performance and longevity of rechargeable batteries.