Who knows if you can disable the fast loading? The smartphone charges really fast and the battery is also very warm. In itself a cool thing, but certainly not good in the long run.
Take a power adapter that can't provide a sufficiently large power, for example, only 10 watts
If you look at the back of the power plug you see output
eg. U = 5 volts / I = 2Ampere → correspond to P = 10 watts
U • I = P