The Gemini MPA-2400 is a Portable Party Speaker that can run on AC power or a rechargeable battery. The battery is a 6FM 4.5 12V 4.5Ah/20hr battery that can last up to 18 hours on a full charge. To change the battery, you need to follow these steps:

1. Turn off the power switch and unplug the AC cord from the unit.
2. Locate the back panel of the unit and use a Phillips screwdriver to remove the 9 screws that secure it.
3. Carefully lift off the back panel and set it aside.
4. Disconnect the red and black wires from the battery terminals by pulling them gently.
5. Remove the old battery from the battery compartment and dispose of it properly.
6. Insert a new battery of the same type and model into the battery compartment and connect the red and black wires to the corresponding terminals.
7. Replace the back panel and secure it with the 9 screws.
8. Plug in the AC cord and turn on the power switch to charge the new battery.