Paul Jones / Android Authority
TL; Dr
- Android 15 is set to change the threshold that determines whether a charger is considered fast, from a paltry 7.5W to a more reasonable 20W.
- The operating system has long considered any charging speed of at least 7.5W to be fast, which is far, far below what actual fast chargers can deliver these days.
- However, the change is not yet live in the latest Android 15 beta, so chargers that deliver 7.5W of power will still be perceived as fast on Pixels.
The smartphone industry is incredibly competitive, so sellers have to do everything they can to convince people to buy their products. One of the ways smartphone manufacturers try to make their products stand out from the rest is to increase charging speed. The fast charging arms race has reached a point where there are even some devices that can get a ridiculous 240W of power from a charger. But without some kind of UI indicator, most users have no way of knowing how fast their phone is actually charging.
While Android displays a small message at the bottom of the lock screen when a fast charger is detected, the problem is that Android considers any charger that delivers at least 7.5W of power to be “fast”. This makes it difficult to tell whether a given charger — say, a public charging station at an airport or a USB port on a laptop — is actually charging your phone quickly. Fortunately, Google is finally looking to fix this problem in the upcoming Android 15 update by changing the threshold that determines whether a charger is rated as fast.
Android 15 Fast Charging Notification: How It Works
Currently, the way Android determines whether a charger is “slow”, “normal” or “fast” is pretty simple. Android, through the health HAL, receives information from the battery and charging circuit, such as current and voltage. If the power (which is determined by multiplying the current by the voltage) being delivered to the phone is below 5W, then the charger is considered “slow” and the message “charging slowly” is displayed on the lock screen. If the power is above 7.5W, it is considered “fast” and the message “fast charging” is displayed instead. If the power is between 5 and 7.5W, the charger is seen as ‘normal’ and the lock screen just says the phone is ‘charging’.
These are the default charging speed thresholds in AOSP, and although they can be configured by smartphone manufacturers, Google has yet to change them for its own Pixel devices. For reference, here is a snippet from frameworks/base/packages/SettingsLib/res/values/config.xml file showing AOSP load speed thresholds:
Code
<!-- Threshold in micro watts below which a charger is rated as "slow"; 1A @ 5V -->
<integer name="config_chargingSlowlyThreshold">5000000</integer>
<!-- Threshold in micro watts above which a charger is rated as "fast"; 1.5A @ 5V -->
<integer name="config_chargingFastThreshold">7500000</integer>Google is finally aiming to increase the fast charging threshold from 7.5W to 20W. This is proven by the fact that in the latest Android 15 beta update, it added a new configuration named config_chargingFastThreshold_v2 this is set to 20000000 (20W in microwatts).
Code
<integer name="config_chargingFastThreshold_v2">20000000</integer>However, Android does not yet use this higher threshold. Load speed thresholds are read from BatteryStatus class of SettingsLib, which after previewing in the latest Android 15 beta has not yet been updated to read the new threshold. It is likely that in a future Android 15 beta, Google will update BatteryStatus class to read the new config_chargingFastThreshold_v2 value instead config_chargingFastThresholdtherefore changing the threshold used to determine when to display the “fast loading” text on the lock screen.
Of course, this is a fairly minor change in the grand scheme of things, especially considering that there was nothing stopping other manufacturers from changing it already. I don’t know how many have, but Google certainly hasn’t, which is a shame since its phones have long been able to get more than 7.5W of power through their chargers. The Google Pixel 8, for example, supports 27W wired charging in the base model and 30W in the Pro model. Once Android 15 changes the charging speed threshold, Pixel users will have a better idea of what chargers they should actually use while on the go.
