@Sep10trion
Sega Engineer: "But it worked for the SegaCD!"
In seriousness, it SHOULD have worked fine. The amount of power needed to maintain data in SRAM is very low. Like, less than the battery's self-discharge rate levels of low.
The real-time clock is the largest power draw. A good RTC should deliver wristwatch-like battery life, but the Saturn RTC is ... not good about power draw, to put it mildly, and it straight-up MURDERS that coin cell. I'm curious what went wrong.
@EOTFOFYL It wasn't ghetto, it was kind of the standard way to preserve data if you didn't have access to magnetic media, or didn't want to take the performance hit. The technique predates affordable flash memories. (I've got a "SSD" from the mid-80s that uses battery-backed SRAMs, and the technique wasn't new then.) It is why game cartridges could get away with a non-replaceable battery.
That one PCI card needed such a large battery because DIMMs use DRAM, which requires significantly more power to maintain data than SRAM.