How to Replace Batteries from 4 AA batteries To 1 Or 2 Mobile battery

4 AA batteries cause me many problems :

1- many times of charges in few time

2- low power all time

3- open slot of batteries, remove to charge and install it

* and many other reasons

* so I want to Replace in safely way the system of batteries from 4 AA batteries to 1 or 2 mobile battery

• mobile batteries is easy to charge, install and small size.
• I think It can put in the same slot by few readjust