Trickle Charge
Power & ChargingA low-current charging mode used to safely top off a battery at near-full capacity.
Once a lithium battery reaches about 80%, the charger switches from fast constant-current mode to a trickle (constant-voltage) mode to avoid overcharging. This is why the last 20% takes disproportionately long. Some devices let you cap charging at 80% to extend battery lifespan by avoiding trickle charging entirely.