Why does The Charging Speed Drop Sharply after The Battery is Fast Charged to 80 Percent of Its Capacity

After years of application and development of batteries, in practical applications, battery technology engineers generally agree that during the charging process, when the battery is nearly fully charged, the charging circuit controls the charging current to decrease, thus achieving the goal of protecting the battery and extending its service life.But why does the charging speed drop sharply after the battery is fast charged to 80% of its capacity ? Actually there are three main reasons  .

1.Battery Protection: In the final stage of charging, the current and voltage are adjusted to reduce battery heating and internal chemical side - reactions, slow down the rate of lithium battery aging, and extend the lithium battery lifespan. For example, fast charging with a high current accelerates the migration of lithium ions inside the battery, which may lead to the formation of lithium dendrites. Reducing the charging speed can effectively mitigate this.

2.Over - charging Prevention: When the battery's charge is approaching full capacity, continuing to charge at a fast - charging speed can easily cause over - charging, leading to safety issues such as battery swelling and fire. Reducing the charging speed allows for more precise control of the charge amount, ensuring the battery is not damaged by over - charging.

3.Battery Management System Limitation: To ensure the charge balance of each battery cell in the battery pack and avoid over - charging or over - discharging of individual cells, when most lithium battery cells approach 80% of their capacity, the battery management system will reduce the charging speed to perform fine - tuned charge balancing.

Carrie 

poeae@liliangbattery.com

www.liliangbattery.com