I recently bough an XT-class computer. Inside it had a 1984 model of Quadram Quadboard multi-function 8-bit ISA card.
I noticed it had a soldered in Vatra Ni-Cd rechargeable battery on it. Those batteries often leak acid when fully discharged. The acid destroys PCB tracks and makes restoring a chore.
My cards battery didn’t leak yet, but I decided to remove it anyway.
I replaced it with CR2032 - a non-rechargeable lithium coin cell. I installed it in series with a diode I removed from a dead motherboard. The diode is probably schottky, since voltage drop is only about 0.3V.
More infiromation, manual and drivers can be found here.