Battery Usage
By Chris De Herrera, Copyright 2002
Revised 7/15/2002

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Battery Design

This article discusses the  battery usage of the Pocket PC and how it affect users.  Currently the Pocket PC 2002's use either Lithium Polymer or Lithium Ion main battery.   In almost all Pocket PC 2002's, do not use a secondary battery for memory retention. 

Battery Life

Currently, the Pocket PC 2002 users have to recharge multiple times per week of average use. If they are power users, they are probably charging daily due to the additional power requirements of peripherals like Ethernet or Modems. Right now users are experiencing from 2 to 12 hours of use depending on their device and how they use it. I believe that the battery life of the Pocket PC should reflect from 2 to 3 hours of daily use for a total of 21 hours per week.  Also some units discharge the battery more quickly than others even though the user is not using the Pocket PC so make sure you watch the amount of power left.

Battery Warnings

Microsoft decided to notify the user when they turn the Pocket PC on that the main battery is low when the power remaining is 40%.  Then the system will warn the user at 20% if the user turns the Pocket PC on.  So the user will never know that their battery is nearly drained until they turn their Pocket PC back on.  I believe that Microsoft should change the battery notification to be a true alarm that beeps loud (ie: overrides the volume setting) and flashes the LED incessantly until the unit is charged like a cell phone does.  Also, warning the user at 40% power remaining is too high.  I believe that the percentages should be closer to 20% and 10% respectively or allow the user to adjust it like Microsoft does on laptops.

Memory Backup - Why We Need It

All of the Pocket PC 2002's use SDRAM for program storage and program execution.  SDRAM requires that the system maintain power to the ram in order for the contents of the memory to be retained even when powered off.  This is what allows the Pocket PC to be instantly powered back on.   If a manufacturer chose to use Flash for storage instead of SDRAM, then users would feel confident that all their data will be retained if the battery is dead, except for whatever data is not saved.

Memory Backup - How Long?

The current standard for memory backup is to provide for 24 hours of memory retention when the Pocket PC says that there is no more battery left.  While this sounds like it would be sufficient, there are multiple reasons that this is not enough time for users.  Further since the battery is the same as the main battery, when the main battery fails, all memory is lost.  I believe this must be expanded especially when users are using the Pocket PC 2002 Phone Edition which users will expect that their data is retained just like existing cell phones even when the battery is fully discharged.  The one Pocket PC 2002 that is an exception in terms of memory backup is the Casio E-200 and the HP Jornada 56x which uses a secondary CR-2032 backup battery.  The Casio E-200 can retain your data for 7 days and the HP approximately 3 days.  The big difference is that HP designed their Pocket PC so that the main battery is fully drained and all memory backup is done by the coin cell.  This means, when you fully discharge your HP, you are also discharging the coin cell as well.  Also, be aware that the coin cells are not rechargeable so consider changing them from time to time for optimal efficiency.

The Needs for Standards?

Right now each hardware vendor creates their own battery and their own power supply.  I believe it is in the best interests of consumers that all batteries be user removable for replacement and that they be standard.  Also, using standard pinout, voltage and amperage would provide users with more options for recharging their Pocket PCs.

Conclusion

Overall, the power management of the Pocket PC allows users to have a good experience with their Pocket PCs just so long as they use them sparingly.  I hope that manufacturers will consider making some of these changes in their future designs to accommodate the needs of users for retaining their data for extended periods of time.

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