Well, if it's any help....if you still have the 486, that was my first 486 hard disk and I still remember the CHS and can guide on the CMOS battery issue as well....
MAXTOR 7120AT
HEADS= 936
CYLINDERS = 16
SECTORS = 17
PRECOMP = 0 or 65535 (depending on your BIOS)
LANDZONE = 936
If you could not find a CMOS battery inside, did you see any chips that said "Dallas" or looked similar to below under a different name (more people made these chips than just Dallas, such as BENCHMARQ, Intersil, ST, and so on).
PS: I Can remember the CHS because my first 486 in 2001 had no CMOS battery for the first six months, and I had to put in those numbers EVERY TIME I used that computer. It was really the first computer I really did any actual serious work on past a memory upgrade.