determining, by a user device, that a charging adapter is connected to the user device, the user device comprising a first battery and a power management integrated circuit;

determining, by the user device using a power management integrated circuit, that the charging adapter has a rated maximum output current value;

determining that the rated maximum current value is greater than a first maximum charging load value of the first battery;

charging the first battery at the first maximum charging load value with a first charging current;

determining that a second battery is connected to the user device, the second battery having a second maximum charging load value that is greater than the first maximum charging load value;

determining a second charging current value that is a difference between the rated maximum current value and the first maximum charging load value;

charging the second battery at the second charging current value with a second charging current;

determining that the second charging current value is less than the second maximum charging load value;

increasing the second charging current to a third charging current value, wherein the third charging current value is less than the second maximum charging load value;

determining, by the user device using the power management integrated circuit, that an input voltage at the user device is equal to or greater than 4.75 volts;

increasing the second charging current to a fourth charging current value, wherein the fourth charging current value is less than the second maximum charging load value;

determining that the input voltage is less than 4.75 volts; and

reducing the second charging current to a fifth charging current value.