APC RBC18 is the replacement battery cartridge for PS250, PS250I, PS450, and PS450I UPS systems. It is supplied as a complete set of tested and charged batteries, so you can return the UPS to service quickly without piecing together individual cells or guessing at battery condition. For infrastructure teams, the value is operational control. The cartridge is user-replaceable and hot-swappable, which means battery maintenance can be handled with less interruption to protected loads. That matters when the UPS is supporting network gear, point-of-sale systems, or other equipment that cannot tolerate avoidable downtime. RBC18 also includes free freight back to APC for disposal of used batteries in the US, reducing the friction of end-of-life handling. If you are maintaining installed APC systems and need the correct battery format rather than a generic substitute, RBC18 delivers the right fit, verified battery preparation, and a cleaner service process.