This Battery backup is for use with the "Solar w/ Battery Backup Capability" Solar Day units. Simply mount the battery box in your closet and relay to your Solar Day fixure and you will enjoy the same full-spectrum light from the Solar Day even after the sun goes down. The battery is charged by the solar panel; thus, eliminating any charging from the utility grid. Includes: - GEL Cell Battery - Charge Controller - On/Off Switch - Built in Circuit Breaker - Mounting Screws