I was a little bit baffled at the microUSB charging port given the prevalence of USB - C nowadays, but it's not a bad thing — you could very easily re-purpose
an old cellphone charger to top off your battery if you have an Android phone.
Because the Pi is a micro computer and not simply a
cellphone getting a battery topped off, you need to use a high quality
charger with stable power delivery that provides a consistent 5v with at least 700mA minimum output for
older model units and 2.5 A for the Pi 3.