Charging speed slowing down as a battery approaches full capacity is primarily due to the way ions move within the battery and the design of the charging process itself.
Reasons for Slowing Charging Speed
- Chemical Reactions and Ion Movement:
- In the early stages of charging, ions can move freely and quickly within the battery. However, as the battery nears full capacity, the movement of ions becomes more restricted due to the increase in charge density. This results in a decrease in the rate at which the battery can absorb additional charge.
- Charging Process Design:
- The charging process for lithium-ion batteries typically involves two stages: constant-current (CC) and constant-voltage (CV). Initially, during the CC phase, the battery charges at a constant current, allowing it to fill up quickly. As the battery reaches a certain state of charge (SOC), typically around 80%, the charger switches to the CV phase. In this stage, the current tapers off to maintain a constant voltage at the battery terminals, preventing overcharging and potential damage.
- State of Charge (SOC) and Charging Speed:
- Batteries charge most efficiently when they are partially discharged. As the battery approaches full capacity, the charging speed naturally decreases to ensure safety and longevity. This reduction in speed also helps to optimize energy delivery and prevent overheating.
- Technical Limitations and Safety:
- Fast charging can cause heat buildup, which may reduce the battery’s lifespan. By slowing down near full capacity, the charging process helps to mitigate these risks and maintain the battery’s health over time.
In summary, the slowing down of charging speed as a battery reaches full capacity is a deliberate design feature to protect the battery from overcharging, manage heat buildup, and ensure optimal performance and longevity.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/why-does-the-charging-speed-slow-down-as-the-battery-approaches-full-capacity/
