Hi,   Yes, the S100 is the onboard RAID and H700 card would be an upgrade. H700 would definitely a better RAID controller. Imagine example an onboard GPU and a GPU card.   The CMOS battery would be a CR2032. If the system is left idle without power for a very long time, the CMOS battery would not last, so I'm guessing the BIOS will not retain it's previous settings, which by default SATA is set to RAID mode. That enables the on board S100.    At the moment, if the system is working fine, you would probably save a trip over. That depends on you. 
I just scored me an old PowerEdge T310 that I'm planning to put into service.I'm rather new to this series and I find the boot sequence perplexing to say the least. Notably the messages around the hard disc support. Up from it's worth saying this server runs perfectly fine currently under Ubuntu 19.04. No real issues, just a few oddities in terms of understanding the boot sequence and mini LED screen messages.For now I'd like to ask about he HDD related boot messages. Here's what's on the screen as it boots: What's puzzling me is what all this means. Notably: What's going on here. Why does it take 50 seconds tpo find my virtual drive? Why does it report a missing BIOS?I can't find any clues in the manual or on-line. I'm a bit bamboozled.  
Understanding the boot sequence of a PowerEdge