weird thinkpad battery behavior

[mathfeel]

I have a thinkpad T42. In addition to the battery that came with the system, I also bought one of the model that fits into the dvd-bay (since I don't use the drive that much). In Windows, I got good battery hours out of both batteries. In linux, when I unplug the computer, the additional battery appears completely discharge (as reported by battery monitor software in linux and Windows). Any idea to what's going on?
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"In heaven all the interesting people are missing"
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