What is advantage/ disadvantage of 12, 24, 48 volts?

Advantages for different voltages are as follows.  Higher voltage battery bank can be more efficient, due to smaller cable sizes which can lead to less current, less voltage drop and less heat.    Also, higher voltage battery banks typically have multiple batteries in series to increase the voltage; this increases the amount of charge and discharge cycles your batteries are capable of handling. Disadvantages for different voltages are as follows, lower voltage battery banks are typically used for smaller systems and these battery banks may be less efficient and may consume more DC power than higher voltage systems.