I always charge in an external charger because it is more convenient for me to do so. Plus I believe it is safer as I don't want to damage my radio if something went wrong with one of the batteries. But many people have great success and always charge from inside the radio. So it is a materr of personal choice and what works for you. I have several different scanners, so an external charger works best for me. The most important thing is to buy a quality set of batteries to start with.