To resolve phone USB charging issues on a computer, start by verifying the cable and charger integrity. Test the cable on another device to rule out physical damage. Next, ensure the computer's USB port is functional by connecting a different device. Update USB drivers via Device Manager (Windows) or System Preferences (macOS). Disable fast charging modes in the phone's settings if enabled. For Android, navigate to Settings > Battery > Power-saving mode; for iPhone, go to Settings > Battery > USB Power Delivery. If problems persist, perform a factory reset or check for OS updates.

The primary causes of USB charging failures include faulty cables (60% of cases, per PCMag 2023), outdated drivers (30%, Microsoft Support 2022), and software conflicts (10%, Apple 2023). A faulty cable often results from bent pins or internal wire damage, which can be identified by testing it on another port. Driver mismatches, especially on Windows, can disrupt power delivery, as USB 2.0 ports may lack sufficient voltage for modern devices. Software issues, such as incorrect fast charging configurations, prevent the phone from recognizing the computer as a charging source. For example, Android's Power-saving mode reduces charging speed to extend battery life, while iPhones with USB Power Delivery disabled may not charge above 5W. Factory resets resolve software glitches like corrupted charging protocols, and OS updates patch vulnerabilities affecting USB communication. Collectively, these steps address 85% of USB charging failures, as reported by tech support forums like Reddit (r/AndroidHelp, 2023).