After measuring the power consumption when running off the AC adapter, we had carried out the same results when the notebook was running off its battery. The battery discharge rate was acquired from /proc/acpi/battery/BAT0/state. The R52 was running BIOS version 1.25 (76ET65WW) and its power settings were set for "Maximum Performance" when running in AC mode and when running on the battery was configured for "Maximum Battery Life". The battery that the ThinkPad R52 used was a Sanyo IBM-92P1075. When running off the battery and idling, Ubuntu 7.10 was averaging 22.26 Watts for its discharge rate while Ubuntu 6.10 was discharging the least with 19.35 Watts.
While running on the battery and under load, Ubuntu 7.10 wasn't discharging the battery the fastest but in fact it was Ubuntu 7.04 that was feeling power hungry. Like with our AC tests, under load the older Ubuntu releases (5.04, 5.10, 6.06.1) were consuming less power.