For most modern smartphones, the recommended charging power is 5 volts and 2 amps (5V/2A). However, some devices may support higher charging power, such as 9 volts and 2 amps (9V/2A) or 12 volts and 1.5 amps (12V/1.5A).

Several factors can lead to the slow charging of a phone:Low-power charger: If you are using a charger with a low-power output, such as an old or low-quality charger, it will charge your phone slower than a more powerful charger.USB connection: Charging through a computer's USB port or using a low-quality USB cable can slow down the charging process.Background processes: Running numerous apps or resource-intensive tasks while charging can reduce the charging speed.Battery age: As batteries age, their charging speed may decrease, leading to slower charging times.Temperature: High ambient temper

In most cases, phone chargers from the USA are compatible with different voltage standards used in other countries. However, you may need a plug adapter as the socket format may vary.