#2244 HIGH First D: Battery rollover palette inaccurate

[Zarro Boogs per Child]

#2244: Battery rollover palette inaccurate
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  Reporter:  Eben    |       Owner:  edsiper               
      Type:  defect  |      Status:  assigned              
  Priority:  high    |   Milestone:  First Deployment, V1.0
 Component:  sugar   |     Version:                        
Resolution:          |    Keywords:  review-               
  Verified:  0       |  
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Comment(by rsmith):

 Replying to [comment:9 edsiper]:

 >this case the information is not exported, talking with Richard he said
 that the only way for the moment is try to match the battery model with
 the http://wiki.laptop.org/go/Laptop_Batteries information Spec.

 > Marco, can be done this in this way?, I mean have a static information
 about the known batteries/models and their respective mAh? in order to get
 the calc ?

 Some points you will need to consider:

 1) This info is not static.  It decreases after every discharge/charge
 cycle.  The OLPC design requriment is that 50% of the capacity is left
 after 2000 cycles.  Thats about .025% decrease per cycle (If you assume it
 linear across the range).  So while this might be accurate for new
 batteries it will not be so accurate for older batteries.  If you let the
 charge on the batteries move outside the mfg suggested levels it will also
 degrade the capacity.  A good example of this would be to leave the
 batteries on the shelf and let them totally discharge.

 2) The capacity changes based on the ambient temp.

 The reason you can get this from ACPI is that ACPI requires the use of a
 "Smart" battery.  "Smart" batteries have a microprocessor inside the
 battery with the sole purpose of keeping accurate information on the state
 of the battery.  The XO does not have a smart battery it has a sensor
 inside that provides a lot of the raw info.  This info is used by the EC
 to make charge estimations but the calculation is complex and without
 battery history hard to do accurately.

-- 
Ticket URL: <https://dev.laptop.org/ticket/2244#comment:11>
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