Motherboards from the late-1990s to today utilize a CR2032 cell to maintain the system’s clock and settings when turned off. However, the older NiCD or NiMH barrel batteries made by Varta have proven to be troublesome, leaking and damaging boards over time. The Bad Idea Barta Board humorously references these destructive batteries. Replacing these batteries can be done with a CR2032 coin cell holder or a Tadrian 3.6 V Lithium cell, among other options. The author prefers using a 3× AA battery approach for its ease of swapping batteries and avoiding voltage issues. Detailed instructions and helpful resources are available for those looking to replace their motherboard batteries.
https://rubenerd.com/building-a-replacement-486-cmos-motherboard-battery/