www.amazon.com/.../B0045ZNJJU www.impactcomputers.com/u8735.html The battery only keeps data in the write cache that has not yet been written to the disks ACTIVE in the cache memory in the event of a sudden shutdown/power outage.  Without the battery, the controller simply turns OFF write caching to protect the integrity of your data.  Having write caching off WILL affect performance. To replace it, all you do is simply unclip and disconnect the existing battery, attach and clip the new one in its place.  It is very easy to reach, as it is on top of the drives, just under the top cover.
Openmanage says it has failed. Can I get a part number please? How critical is the battery to normal function? In a failed state does it affect performance? And once I get the new part, what is involved in installing it? Thanks, Mike
PE1950 PERC 5/i Battery Failed.