Hello [NAME], PERC's battery is for cache. Hardware RAID controllers utilize cache (a temporary repository of information) for its normal operation. The normal operation cache is comprised of DRAM memory, which like system memory, only retains data while powered. However, newer controllers utilize NVCache, which is utilized when the server is powered off. NVCache memory contains both DRAM memory (for normal operation) and flash memory (non-volatile). The controllers battery (if operational) powers the DRAM memory during a power loss so the contents can be copied into the flash memory for indefinite storage. Regards.
Hi,It`s really basic question but, What is the main purpose of the battery that located  on the DELL PERC cards?Backup of ?     
Basic question about DELL PERC cards battery