PE R415 with H700, replacing failed drive and controller battery

Hello all,

We have an older PowerEdge R415 that has an PERC H700 Integrated controller, with 3 cabled SATA drives, configured in a RAID 5 VD.  And the system runs VMWare ESXi 6.5.   I am not certain if these drives are hot swappable, but, I was assuming that they were not.

When I recently had to reboot rebooted this machine, I got an alert that "Some configured disks have been removed from your system, or are no longer accessible"

I have a replacement HDD to match the drives currently in the system.   I attempted to booth into the controller configuration after boot to verify which disk was faulty, since they don't have front panel LEDs, however, I got a message stating:

"Entering the configuration utility in this state will result in drive configuration changes."   

So I backed out at that point. 

Previously I had installed the OMSA vib in ESXi, on this machine, but when I attempt to access it via Server Administrator on another computer, after logging in, the main OMSA screen only partially loads and doesn't display any info.

  Any suggestions on next steps?

Also, I get a message during boot that "The battery is currently discharged or disconnected".

I have what I believe to be the correct replacement battery, however, I don't see where the battery is inside the chassis.     Any advice on this would be appreciated as well.

Thank you