I just purchased an 12-cell 8800mAh battery to replace the 6-cell 4400mAh unit that came with my Compaq C700. After fitting the new battery, I'm seeing exactly the same ACPI info as I saw with my old battery:
present: yes design capacity: 4752 mWh last full capacity: 4752 mWh battery technology: rechargeable design voltage: 10800 mV design capacity warning: 475 mWh design capacity low: 256 mWh cycle count: 0 capacity granularity 1: 264 mWh capacity granularity 2: 3780 mWh model number: Primary serial number: battery type: Lion OEM info: Hewlett-Packard
Is it possible that the ACPI info is in error, or is this 12-cell battery really no more capacious than my old six-cell?
Followup: In use, the battery is performing the way I'd expect a 12-cell to perform, but it is definitely returning the wrong info to ACPI. It looks like what's happened is that the manufacturer has directly copied the data being reported by the genuine HP batteries.