Since maintaining a full charge on a lithium-ion battery is detrimental to its long-term capacity, Adaptive Charging will delay charging at 80% charge as long as an ML model predicts that the charger will not be unplugged within 2 hours.
Charging is delayed via the Battery Sustainer feature in the EC. This is run via the command ectool chargecontrol normal <lower> <upper>. lower is the lower limit battery percent, and upper is the upper limit for the battery percent. The battery will charge and discharge between these two charge values while the Battery Sustainer is active. If lower and upper are the same, the charger will idle (no current to or from the battery) while at that charge.
The prediction of when the system will be unplugged from the AC power source is handled via the org.chromium.MachineLearning.AdaptiveCharging DBus service. The power manager requests predictions from this service every 30 minutes. It creates a probability for each of the next 8 hours, plus a prediction for anytime greater than 8 hours, on whether the AC charger will be unplugged then. If the largest probability is at least adaptive_charging_min_probability, charging will be delayed up until 2 hours before the charger is expected to be unplugged (the hour associated with the highest probability).
The user will be notified of any delays when the display_battery_percentage reaches 80%, if charging will be delayed.
The feature is enabled by default for systems with firmware support for maintaining specific battery charge percentages, and waking from sleep on AC plug and unplug.
The Settings app contains a toggle for enabling/disabling the feature under the Power section. This triggers a policy update via the PowerManagementPolicy proto for the power manager. These fields are available to Chrome to manage Adaptive Charging settings:
adaptive_charging_enabled - bool that enables/disables Adaptive Charging.adaptive_charging_hold_percent - Change the battery percentage at which to delay charging. Default value of 80. Valid values are within [1, 99].adaptive_charging_min_probability - Change the min probability that is required from the prediction to delay charging. Default value of 0.2. Valid values are within [0.0, 1.0].