Power consumption on X61S increases with bigger battery?

[kryft]

Hi,

I'm running Ubuntu 7.10 on an X61S. The computer came with the four cell slimline battery, but I just bought an eight cell battery. When I use the eight cell battery, the ACPI power consumption estimate (as reported by powertop) goes up several watts compared to the figure I get for the four cell battery.

Is this possible? It seems very strange that the power consumption should depend on the battery. The only other explanation I can think of is that the ACPI power consumption estimate is wrong.