You can use the BPALK alkaline battery pack to power your CR800, CR850, CR1000X, or CR3000 dataloggers, and their peripherals. You can also use it as a separate auxiliary 12 V power supply to power remotely located sensors or peripherals. The system must have a common ground. The BPALK consists of eight replaceable D-cell alkaline batteries, battery connectors, and a temporary 12 V AA alkaline battery pack used during D cell replacement. The temporary battery pack requires eight AA-cell batteries (not included).