[Galaxy S24 Ultra] Fast Charging issue

Hello @spicy_llama329. Welcome to the Samsung Community! It is completely understandable to feel stressed when a device like the Galaxy S24 Ultra behaves unpredictably, especially when you love the phone and want to avoid the hassle of a complete data wipe. Since you have already tackled the standard reboots and background app management, let's explore a few specific system paths and diagnostics that might help restore your charging speeds:

Clear USB System Cache: Sometimes the system software responsible for managing the USB port handshake gets stuck. Go to Settings > Apps, tap the "Your apps" filter icon (next to the search bar) and toggle on Show system apps. Search for USBSettings, tap on it, select Storage, and tap Clear Cache.

Toggle Charging Settings Manually: Navigate to Settings > Battery > Charging settings. Verify that Fast charging is toggled on. If it is already on, toggle it off, restart your phone, and then switch it back on to force the system to refresh the setting.

Test in Safe Mode: Swipe down from the top of your screen to open the Quick Settings panel, then tap the Power icon in the top right corner. Touch and hold the Power off icon on the screen until the Safe Mode prompt appears. Tap Safe Mode to confirm. Once the phone reboots, plug in your charger to check the speed. If it works, a third-party app is causing interference. Restart normally to exit.

Run Embedded Port Diagnostics: Open the pre-installed Samsung Members app, select the Support tab at the bottom, and tap Phone diagnostics. Run the tests specifically for the USB Connection and Battery status to see if the hardware flags any internal negotiation errors.

For a complete step-by-step breakdown of power profiles and official recommendations, you can review the Samsung Support Guide on Galaxy Battery Charging.
Please keep us updated on whether the app cache or Safe Mode test yields any changes so the Community can continue to assist you!