Microsoft removed native SCSI support with 2008 R2, but Dell provided 2008 R2 drivers for the PERC. Those drivers work for installing Server 2012 as well. Memory/battery message: stop everything and order replacement memory for the RAID controller, part number 4D554. Nothing related to the OS will work (install, repair, etc.) until you do. This issue is very specific to the PERC 4e/Di on the 28x0. The 2850 is not 12 years old. It first started shipping 10 years ago.
Okay, I have a PE 2850 that was loaded up with Windows Server 2012 early last year in connection with our Windows 7 Upgrade Project. While I know that Windows Server 2008 was the last version from Microsoft to officially support SCSI interfaces like the PERC 4E/DI RAID card included in the 2850, I was able to get around it by first installing 64 Bit Server 2008 with the SCSI drivers and then doing an inline upgrade to Server 2012.  Everything ran just fine for the past year and a half, but when I came into work yesterday, the server had crashed and was sitting at the BIOS screen with the following error message: Memory/battery problems were detected. The adapter has recovered, but cached data was lost. Press any key to continue. I pressed enter and the server proceeded to move to a preparing to repair Windows screen where the progress bar quickly moved about 80% of the way and then froze for over an hour. Subsequent attempts to reboot into safe mode led to the server freezing at the Windows logo screen for several minutes before once again rebooting to that same error message. I can pull up the RAID management and see my partitions still there, and I even loaded up my drives in an older PE 2600 to check for consistency on the Logical Drives (no issues found). However, the older 2600 is 32bit architecture and it won't even attempt to boot into the OS. At this point, I am really just trying to get a full backup of my system. I don't mind getting a new server, but I just don't want to keep throwing money at this 12 year old piece of equipment without knowing if it will work or not. The problem is that 2012 uses ReFS, and none of the recovery programs I have found can access my logical volumes. Booting off the OS Installation Disc to recovery console also doesn't work, as the OS Disc does not include native SCSI drivers to be able to see the OS partition or the Data partition.  I think I am going to call some data recovery services tomorrow, but thought I would check here for any ideas first. Any input is greatly appreciated. 
Poweredge 2850 Windows Server 2012 not Booting