power_manager/docs/adaptive_charging.md - third_party/platform2 - Git at Google

 # Chrome OS Adaptive Charging

 ## Delaying Charge

 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.

 ## Prediction

 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).

 ## Notifying the User

 The user will be notified of any delays when the `display_battery_percentage`
 reaches 80%, if charging will be delayed.

 ## Enabling

 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].

 ## Slow Charging

 As quick charging of a lithium-ion battery is detrimental to its capacity and
 ability to retain charge over time, slowing down charging where possible is
 beneficial for long-term battery health. Slow charging is a feature implemented
 in Adaptive Charging to limit the charge current to the battery when charging
 commences after the period of delay at 80% charge.

 When slow charging is enabled, Adaptive Charging will delay charging at 80%
 charge up until 3 hours before the charger is expected to be unplugged. A charge
 current limit of 0.1C (i.e., 10% of the battery's design capacity per hour) will
 be set when charging commences after the delay period. If the unplug time
 prediction moves earlier while slow charging, resulting in insufficient time to
 finish charging using the limited charge current, the charge current limit will
 be removed.

 The charge current limit is set via the EC and is run using the command `ectool
 chargecurrentlimit <max_current_mA>` where `max_current_mA` is the maximum
 charge current that will be supplied to the battery.

 The slow charging feature is yet to be launched and will be rolled out gradually
 via Finch, the Chrome experimentation framework.

 ## Charge Limit

 A separate solution to improve battery health than Adaptive Charging is Charge
 Limit. This feature always prevents charging above the Adaptive Charging hold
 percent, which is 80% by default. This is a more aggressive approach to
 improving battery health, but it has a larger benefit than Adaptive Charging.

 This feature is useful for the lab and other environments where you never need a
 full charge for the battery.

 [Adaptive Charging]: https://chromium.googlesource.com/chromiumos/platform2/+/HEAD/power_manager/powerd/policy/adaptive_charging_controller.h
 [PowerManagementPolicy]: https://chromium.googlesource.com/chromiumos/platform2/system_api/+/HEAD/dbus/power_manager/policy.proto
	# Chrome OS Adaptive Charging

	## Delaying Charge

	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.

	## Prediction

	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).

	## Notifying the User

	The user will be notified of any delays when the `display_battery_percentage`
	reaches 80%, if charging will be delayed.

	## Enabling

	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].

	## Slow Charging

	As quick charging of a lithium-ion battery is detrimental to its capacity and
	ability to retain charge over time, slowing down charging where possible is
	beneficial for long-term battery health. Slow charging is a feature implemented
	in Adaptive Charging to limit the charge current to the battery when charging
	commences after the period of delay at 80% charge.

	When slow charging is enabled, Adaptive Charging will delay charging at 80%
	charge up until 3 hours before the charger is expected to be unplugged. A charge
	current limit of 0.1C (i.e., 10% of the battery's design capacity per hour) will
	be set when charging commences after the delay period. If the unplug time
	prediction moves earlier while slow charging, resulting in insufficient time to
	finish charging using the limited charge current, the charge current limit will
	be removed.

	The charge current limit is set via the EC and is run using the command `ectool
	chargecurrentlimit <max_current_mA>` where `max_current_mA` is the maximum
	charge current that will be supplied to the battery.

	The slow charging feature is yet to be launched and will be rolled out gradually
	via Finch, the Chrome experimentation framework.

	## Charge Limit

	A separate solution to improve battery health than Adaptive Charging is Charge
	Limit. This feature always prevents charging above the Adaptive Charging hold
	percent, which is 80% by default. This is a more aggressive approach to
	improving battery health, but it has a larger benefit than Adaptive Charging.

	This feature is useful for the lab and other environments where you never need a
	full charge for the battery.

	[Adaptive Charging]: https://chromium.googlesource.com/chromiumos/platform2/+/HEAD/power_manager/powerd/policy/adaptive_charging_controller.h
	[PowerManagementPolicy]: https://chromium.googlesource.com/chromiumos/platform2/system_api/+/HEAD/dbus/power_manager/policy.proto