The answer to the question of how many batteries you need for an 8000 watt amp really depends on the size and type of battery you are using. Generally, a large gel cell or AGM deep cycle battery will have enough power to support an amplifier of this size. Depending on the specifics of your application, it is recommended that you use at least two 12-volt marine/RV batteries in series with each having a capacity rating above 200 Amp Hours (Ah). This would provide enough energy to run your amplifier for several hours without draining too quickly; however, if you’re looking for extended play time then we suggest using four or more such batteries wired in series with each rated at 200 Ah or higher. It is important to note that when installing multiple batteries in series, their voltages must all be equal before connecting them together otherwise one may drain faster than another leading to uneven performance.