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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.

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Could it be a fake part? I'd take it back to the retailer. – RedGrittyBrick May 11 '11 at 14:22
My first thought too. – gerryk May 11 '11 at 15:37
Looks like it's a fake ... waiting to hear back from the seller, who has asked me for all the info (photo of the unit, barcode, ACPI data). – Duncan Bayne May 12 '11 at 22:40
up vote 1 down vote accepted

Each battery pack has a chip that contains all controlers and informations of the pack. This is actually an interface for some driver get the acess to battery features and informations, what i think it is happening is that the battery chip of your 8-cell pack isnt right. What you should do to verify if you have a real 8-cell pack is test it with some battery test tool. I dont know any in specific, but if you take a look at google you will find a lot of god options... I hope it helps..

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