Compaq Portable III - CMOS battery options
OPTION #1
1. Low profile 4-terminal battery module (3.4V battery with diode and resistor) soldered to the motherboard. Part number 107157-001
2. Supporting components for the battery module: Diodes + resistors + transistor
3. MC146818 CMOS/RTC chip in IC socket U77
4. Supporting components for MC146818: Crystal + MC14069 chip + capacitors + resistors
The battery module powers the MC146818 when the computer is powered off.
Photo at here.
The second photo in post #6 at here shows how someone substituted a 3.6V lithium battery in place of the battery module.
OPTION #2
1. No battery module
2. Dallas DS1287 CMOS/RTC module (contains a battery) in IC socket U77
2. Zero-ohm links
The battery in the DS1287 powers the DS1287 when the computer is powered off.
Photo at here.
As for fixing a low/dead battery in the DS1287, see here.