CC/CV charging

also: constant current / constant voltage · lithium-ion charging

The standard lithium-ion charging method: constant current until the cell reaches its maximum voltage, then constant voltage while the current tapers off.

A lithium-ion charger first supplies a constant current (the CC phase) until the cell reaches its maximum charge voltage, commonly 4.2 V for many NMC-type cells and around 3.6 V for LFP, then holds that voltage (the CV phase) while the current falls. Charging ends when current drops below a set threshold; lithium-ion cells are not trickle-charged once full.

Charging to a slightly lower voltage, and avoiding long periods at full charge and high temperature, extends cycle life, which is why some products offer limited or "optimized" charging modes. Charging below freezing must be blocked or heavily reduced because it can cause lithium plating and internal shorts.

Charger chips handle the CC/CV profile, but the product design chooses the voltage, current and temperature limits.

Founder takeaway

Set charge voltage, current and temperature limits deliberately from the cell datasheet and your cycle-life goals, and verify them across the full temperature range.

engineer review pending