The RAID adapter may report the following messages:

"Current capacity of the battery is below threshold" indicating that maybe the battery needs to be replaced.  This may be fixed by "relearning" the battery. This will drain the cache battery and charge it a few times to relearn it back up to full charge."

2019-07-29T19:30:01-05:00 <hostname> disk_subsystem[19465]: snlog: sn="##:##:##:##:##:##" id="DS" m="23" c="6" event="DISK_STATUS" category="HARDWARE" ip="10.0.0.1" model="R730xd" msg="Adapter 1; seqNum: 0x00019bb5; Time: Mon Jul 29 20:26:52 2019; Event Description: Current capacity of the battery is below threshold; "

The batteries need to be drained and recharged periodically.  This is not common.

At a CLI prompt as root, run:  megacli -adpbbucmd -bbulearn -aX  (where X is the adapter number).