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How do secondary cells recharge?

Published in Battery Recharging 2 mins read

Secondary cells, also known as rechargeable batteries, recharge by reversing the chemical reactions that occur during discharge. This process effectively restores the cell's chemical energy, making it available for reuse. According to the provided reference, recharging involves applying an external current to reverse the discharging process and convert electrical energy into chemical energy.

Here's a more detailed explanation of how secondary cells recharge:

The Charging Process Explained

The charging of a secondary cell can be understood by comparing it to its discharging process.

  • Discharge: During discharge, the cell produces an electrical current as chemical energy is converted into electrical energy.
  • Recharge: Recharging is essentially the opposite of this. An external power source forces a current through the cell in the opposite direction. This reverses the chemical reactions that occurred during discharge, restoring the reactants to their original state and thus storing electrical energy back into the cell as chemical energy.

Secondary Cell as an Electrolytic Cell

During charging, the secondary cell behaves as an electrolytic cell. This means that electrical energy is used to drive a non-spontaneous chemical reaction. The external electrical source forces electrons to move within the cell, which effectively changes the chemical composition of the electrodes back to their charged state. This contrasts with the cell's operation during discharge, where it functions as a galvanic or voltaic cell, converting chemical energy to electrical energy.

Key Points about Recharging

  • Reversal of Reactions: The fundamental principle of recharging is the reversal of the chemical reactions that produce electricity during the discharge phase.
  • Energy Conversion: Recharging involves converting electrical energy (from an external source) into chemical energy (stored in the cell).
  • Electrolytic Behavior: During recharging, the secondary cell operates as an electrolytic cell, utilizing an external electrical current to drive chemical reactions.

Examples of Secondary Cells

Common examples of secondary cells include:

  • Lead-acid batteries (used in cars)
  • Lithium-ion batteries (used in smartphones, laptops, and electric vehicles)
  • Nickel-metal hydride (NiMH) batteries

Each of these types of batteries has specific chemical reactions that are reversed during recharging, but the fundamental principle remains the same: electrical energy is used to reverse the chemical processes that produce electricity.