What is a convertible power handle and when would it most likely be used? / Should I purchase a diagnostic set with disposable or rechargeable batteries?

Convertible power handles have the capability to use either disposable or rechargeable batteries. It is a lifesaver if you are on call or taking an exam and have forgotten to charge the battery. Also, the convertible handle is very useful when you are working overseas or in areas where it is difficult to find electricity.