Here are practical, OS-level settings and strategies to extend battery life. I’ll separate platform-agnostic tips from quick, actionable steps for Windows, macOS, Android, and iOS.

Platform-agnostic principles (apply to any device)

• Reduce screen power: Lower brightness, use auto/adaptive brightness, shorten screen timeout.
• Turn off radios you don’t need: Wi‑Fi, Bluetooth, NFC, AirDrop/Nearby Share when idle.
• Limit background activity: Close or restrict background apps and background sync.
• Use power-saving modes: Enable “Battery Saver”, “Low Power Mode”, or equivalent.
• Manage location & sensors: Allow location access only while using the app, and turn off high-accuracy GPS when not needed.
• Reduce push & fetch: Set mail/calendar to fetch less frequently or use manual fetch.
• Disable unnecessary notifications, live wallpapers, widgets, and animated backgrounds.
• Restrict high-power features: Turn off always-on displays, haptic feedback, keyboard backlight, and high-refresh-rate display (or lower refresh rate).
• Update sensibly: Keep OS and drivers reasonably up to date (bug fixes improve battery), but avoid battery-intensive beta features.
• Monitor battery usage: Use built-in battery usage tools to find and limit power-hungry apps.

Windows (laptops & tablets)

• Power mode: Start > Settings > System > Power & battery. Set “Power mode” to “Better battery” or “Best power efficiency.”
• Screen: Settings > System > Display → lower brightness and set “Change brightness automatically when lighting changes” if helpful.
• Sleep: Settings > System > Power & battery → set shorter “Screen” and “Sleep” timeouts.
• Background apps: Settings > Privacy & apps > Background apps → turn off background permissions for apps you don’t need.
• Battery saver: Settings > System > Power & battery → enable “Battery saver” automatically at a chosen battery level.
• Graphics: Settings > System > Display > Graphics → set heavy apps to “Power saving” GPU preference when applicable.
• Bluetooth/Wi‑Fi: Turn off when unused via Action Center. Disable Bluetooth devices not needed.
• Startup apps: Task Manager → Startup tab → disable apps that run on startup.
• Peripheral power: Unplug external drives, USB peripherals, and docks when not needed.
• Adaptive brightness & night light: Use adaptive brightness if sensor exists; disable high-power visual effects (System > Advanced system settings > Performance Settings > Adjust for best performance).

macOS (MacBooks)

• Energy Saver / Battery preferences: Apple menu > System Settings > Battery. Enable “Low power mode” (in macOS versions that have it), set screen sleep earlier, and turn off “Enable Power Nap while on battery” (prevents background syncing).
• Display: System Settings > Displays → lower brightness; turn off “Automatically adjust brightness” only if it causes toggling—test which is more efficient for you.
• App Nap & background: macOS has App Nap; for specific apps that drain battery, quit them. In System Settings > General > Login Items, remove unnecessary startup items.
• Bluetooth/Wi‑Fi: Turn off when unnecessary. Disconnect AirDrop, Handoff, or Continuity features if not used.
• Graphics switching: On MacBook Pros with discrete GPUs, ensure “Automatic graphics switching” is enabled so the integrated GPU is used on battery.
• Spotlight & indexing: Prevent constant re-indexing of external drives; add them to Privacy in Spotlight settings.
• Notifications & Widgets: Reduce widgets and limit app notifications that wake display.
• Battery health: System Settings > Battery > Battery Health — enable optimized battery charging if available.

Android

• Battery saver: Settings > Battery > Battery saver (or Predictive Battery). Set auto-enable threshold.
• Adaptive Battery & Adaptive brightness: Settings > Battery > Adaptive Battery and Settings > Display > Adaptive brightness to let the OS limit rarely used apps and adjust brightness automatically.
• Background activity: Settings > Apps > Select app > Battery → restrict background activity or enable “Put app to sleep.”
• Location: Settings > Location → set apps to “Allow only while using the app” or deny; disable high-accuracy mode (use battery saving) if precise GPS isn’t required.
• Sync & push: Reduce sync frequency or set accounts to manual for noncritical accounts.
• Display refresh rate: If device supports 90/120 Hz, switch to 60 Hz or enable automatic mode.
• Doze & app standby: Keep Doze features enabled (default on modern Android).
• Widgets & Live Wallpapers: Remove resource-heavy widgets and live wallpapers.
• Connectivity: Turn off Bluetooth, NFC, or Wi‑Fi scanning when idle. Use Airplane mode in low-signal areas to prevent radios from constant searching.

iOS (iPhone & iPad)

• Low Power Mode: Settings > Battery → enable Low Power Mode (reduces background activity and visual effects).
• Background App Refresh: Settings > General > Background App Refresh → disable or limit to Wi‑Fi or only necessary apps.
• Location Services: Settings > Privacy & Security > Location Services → set to “While Using” or “Never” for apps that don’t need background location.
• Mail fetch: Settings > Mail > Accounts > Fetch New Data → set to Manual or increase interval; disable Push for nonessential accounts.
• Display & brightness: Settings > Display & Brightness → lower brightness, enable Auto‑Brightness (via Accessibility > Display & Text Size > Auto-Brightness if not visible), reduce Auto-Lock time.
• Cellular/Wi‑Fi/Bluetooth: Turn off when not needed. In poor cellular coverage, use Wi‑Fi or Airplane Mode (with Wi‑Fi on) to save battery.
• Background processes & notifications: Disable nonessential notifications and background refresh; remove widgets you don’t need.
• System services: Settings > Privacy & Security > Location Services > System Services → disable unneeded system location services like Location-Based Apple Ads, iBeacon, etc.
• Optimized Charging: Settings > Battery > Battery Health & Charging → enable Optimized Battery Charging to reduce battery aging.

Quick checklist you can run through now

1. Enable battery/low-power mode.
2. Lower brightness and shorten screen timeout.
3. Turn off unused radios (Bluetooth, Wi‑Fi, NFC).
4. Restrict background app refresh and background processes.
5. Limit location access and set mail to fetch less often.
6. Remove unneeded widgets/animated wallpapers.
7. Use GPU/graphics power-saving settings if available.
8. Unplug external peripherals and close heavy apps (browsers, streaming, games).
9. Monitor battery usage to identify culprits and adjust settings per-app.

When to inspect deeper

• If battery drain is sudden or extreme, check battery usage stats (built-in tools show per-app consumption).
• Consider resetting app preferences or reinstalling a misbehaving app.
• For long-term health, avoid keeping battery at 100% or 0% all the time; use optimized charging features if your OS offers them.

If you tell me which operating system and device you’re using (exact model and OS version), I can give step‑by‑step instructions customized to your device.