I can't remembe who told me, but it was either David or Bob, and actually
he said that on PV the % is rounded up to 100 if it's >= 90. That's why...
Alan Pinstein
Synergy Solutions, Inc.
http://www.synsolutions.com
1-800-210-5293
>At 10:34 PM -0700 1999/05/10, Mike Bitz wrote:
>>Palm OS 3.x's SysBatteryInfo function seems to report an accurate
>>"percent remaining" value on Palm III and IIIx units. However, I am
>>experiencing some strangeness on a Palm V. When the unit is fully
>>charged in the cradle, the percentage is reported as 100%. As soon as
>>the unit is removed from the charger the percentage is reported as 88%.
>>...
>>Is there something special I need to code when dealing with a Palm V?
>
>Nope.
>
>
>>Shouldn't the OS handle any differences?
>
>Yes, and it does (to the best of its ability...)
>
>
>The Palm V uses LiIon battery technology. The discharge curve for this
>type of cell under a Palm V load is extremely flat right up until the
>battery is empty, at which point the voltage dropoff is dramatic. It looks
>something like this (pardon the ASCII graphics):
>
> v 5 -------------------------_
> o 4 |
> l 3 |
> t 2 |
> s 1 |
> 0 time while under load --> |
>
>As a result, using the voltage to measure the battery capacity is
>unrealistic. The difference between 'fully charged' and 'heading south' is
>a few millivolts; nearly within the normal error of the analog to digital
>converter.
>
>To solve this problem and still provide the user with a usable low-battery
>warning, the Palm V OS estimates the amount of energy remaining in the
>cell using a load-over-time function. It calculates this estimate by
>tracking how long the backlight is on, how long the OS is awake and
>processing, et cetera.
>
>I would guess that you're probably just seeing the normal result of the
>averaging function doing its thing (albeit rather slowly). On the other
>hand, it's possible (though unlikely) that your factory-set calibration
>data is inaccurate or has somehow become corrupted, thus the internal (raw
>A->D) voltage reading is so far off it's having a majority impact on the
>averaging function.
>
>Has the unit had this 100% -> 88% behavior since day one? Or does it seem
>like a degenerative behavior similar to the 'memory effect' of NiCd
>batteries where frequent recharge cycles without full discharge cycles
>reduces the battery's maximum capacity? Does the battery seem to discharge
>'faster' than 'normal' or does the 88% calculation stay pretty much
>constant for a very long time during use? How long were you charging the
>unit in the cradle before you removed it and noticed the 88% level?
>
>Regards,
>
>Jim Schram
>3Com/Palm Computing
>Partner Engineering
