Paul Jones / Android Authority
TL;DR
- Android 15 is preparing to tweak the threshold that determines whether a charger is seen as fast, from a measly 7.5W to a more reasonable 20W.
- The operating system has long considered any charging speeds of at least 7.5W to be fast, which is far, far below what actual fast chargers can deliver nowadays.
- The change isn’t live yet in the latest Android 15 beta, though, so chargers that deliver 7.5W of power will still be seen as fast on Pixels.
The smartphone industry is incredibly competitive, so vendors need to pull out all the stops to convince people to buy their products. One way that smartphone makers try to make their products stand out from the pack is to increase how fast they charge. The fast charging arms race has reached a point where there are even some devices that can receive a ludicrous 240W of power from a charger. But without some sort of UI indicator, most users have no way of knowing how fast their phone is actually charging.
While Android does display 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 as “fast.” This makes it difficult to tell whether a given charger — say, a public charging station at an airport or a laptop’s USB port — is actually charging your phone rapidly. Fortunately, Google is finally looking to rectify this problem in the upcoming Android 15 update by tweaking the threshold that determines whether a charger is rated as fast.
Android 15’s fast-charging notification: How it works
Right now, the way Android determines whether a charger is “slow,” “normal,” or “fast” is quite simple. Android, through the health HAL, receives information from the battery and charging circuitry, such as the current and voltage. If the power (which is determined by multiplying current times voltage) that’s being delivered to the phone is below 5W, then the charger is considered “slow,” and the message “charging slowly” is shown on the lock screen. If the power is above 7.5W, then it’s considered “fast,” and the “charging rapidly” message is shown instead. If the power is between 5 and 7.5W, then the charger is seen as “normal,” and the lock screen simply says the phone is “charging.”
These are the default charging speed thresholds in AOSP, and although they’re configurable by smartphone makers, Google has yet to change them for its own Pixel devices. For reference, here’s a snippet from the frameworks/base/packages/SettingsLib/res/values/config.xml file showing AOSP’s charging 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 looking to increase the fast charging threshold from 7.5W to 20W. This is evidenced by the fact that, in the latest Android 15 beta update, it added a new configuration named config_chargingFastThreshold_v2 that’s set to 20000000 (20W in microwatts).
Code
<integer name="config_chargingFastThreshold_v2">20000000</integer>However, Android isn’t yet using this higher threshold. The charging speed thresholds are read by the BatteryStatus class of SettingsLib, which, upon examination in the latest Android 15 beta, has not yet been updated to read the new threshold. It’s likely that in a future Android 15 beta release, Google will update the BatteryStatus class to read the new config_chargingFastThreshold_v2 value instead of config_chargingFastThreshold, therefore changing the threshold that’s used to determine when to show the “charging rapidly” text on the lock screen.
Admittedly, this is a pretty minor change in the grand scheme of things, especially considering there was nothing stopping other manufacturers from changing it already. I don’t know how many have done so, but Google certainly hasn’t, which is a shame since its phones have long been able to receive more than 7.5W of power via 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.
