Before you start turning everything off, there's one quick check that often solves the problem. A simple restart can clear out temporary glitches in HyperOS 2 that might be causing a background process to run wild. Just press and hold the power button for about 15 seconds until you feel the phone vibrate and the screen goes black, then release it to let it boot back up. It's a thirty-second fix that I'd try first.
Check What's Actually Draining Your Battery
Your Xiaomi 15 has a detailed battery usage monitor built right in. Head to Settings > Battery to see exactly which apps have been using power over the last 24 hours. This is the fastest way to spot a rogue app. If you see a social media or game app using 30% or more, that's your likely culprit. You can also tap on Battery Health here to see the overall condition of your battery, which is useful if you've had the phone for a while.
Manage HyperOS and App Behavior
HyperOS 2 is feature-rich, but some of those features are constantly working in the background. A great place to start is with location services. Go to Settings > Location and review which apps have access. For apps like weather or maps, you can often set it to "Allow only while using the app" instead of "Allow all the time."
Next, tackle background activity. Navigate to Settings > Apps > Manage Apps. Pick any app that's showing high battery use and tap on it. Look for the Battery Saver option and set it to "Restrict background activity." This prevents it from updating when you're not actively using it.
Optimize Your Display Settings
The Snapdragon 8 Elite chip and the bright display are powerful, but they can be thirsty. Reducing your screen brightness is one of the most effective ways to save power. You can also shorten the screen timeout. Go to Settings > Display and adjust the "Sleep" setting to 30 seconds or 1 minute.
Make sure Dark Mode is enabled, as it saves significant power on the phone's OLED screen. You can find it in Settings > Display > Colour scheme. Also, consider reducing the screen resolution or refresh rate from the highest setting in the same menu if ultimate battery life is your goal.
Disable System Ads and Unnecessary Features
Some Xiaomi phones have promotional content in system apps, which can use data and battery. You can turn this off by going to Settings > Passwords & Security > Privacy > Advertising services and toggling off "Personalized ads." Also, look for a "Recommendations" toggle in apps like the Mi Video or GetApps store.
Turn off "Raise to wake" or "Tap to wake" if you don't use them, as they keep the proximity sensor active. These are in Settings > Always-on display & Lock screen. For gaming, use the built-in Game Turbo mode. It optimizes performance and can sometimes prevent the chip from running unnecessarily hot, which is a known drain under sustained load.
Connectivity and Syncing Tweaks
When you're not using them, turn off Wi-Fi, Bluetooth, and GPS from the quick settings panel. Your phone won't waste energy searching for networks or devices. Also, check your sync settings. Go to Settings > Accounts & Sync and see if any accounts are set to sync data very frequently. Changing email apps from "Push" to "Fetch" every 30 minutes can make a big difference.
Update Your Software and Apps
Xiaomi frequently releases updates that include battery optimizations and bug fixes. Go to Settings > About phone > HyperOS version and tap "Check for updates." Do the same for your apps in the Google Play Store or GetApps store. An outdated app can sometimes have a bug that causes excessive battery use.
Use the Right Charger and Habits
If your phone didn't come with a charger in the box, make sure you're using a high-quality adapter. For the fastest and most efficient charging, you'll want Xiaomi's official 90W HyperCharge adapter. It's designed to work optimally with the phone's charging system. Wireless charging is convenient, but the 50W wireless pad will generate more heat, which isn't ideal for long-term battery health if used constantly.
Avoid letting the battery drop to 0% regularly. Similarly, you don't need to charge it to 100% every time. Modern batteries are happiest between 20% and 80%. Using the phone while it's fast charging can also make it heat up and slow down the charging process.
When to Consider a Reset
If you've tried all the above and the drain is still severe, a software glitch might be the cause. You can try resetting all your settings without losing your personal data. Go to Settings > About phone > Factory reset > Reset all settings. This will revert your Wi-Fi passwords, wallpaper, and system settings to default, but it often clears up persistent issues.
