Well I've been getting a lot of questions around Battery Power and I thought I'd write something covering battery power on Windows Mobile Devices.   When it comes to a mobile device, Windows Mobile or other, battery power is really limited by 5 things.

1. Processor
2. Screen
3. Radio
4. Hard drive
5. Battery Size / Type

1. The Processor: As we try to get more and more out of Windows Mobile devices, OEMs keep putting in faster and faster processors.  On some devices you'll find that the processors can step up and down power consumption based on usage,  however as we move forward we'll generally see faster processors using more power.

2. The Screen:  The Screen on the Device is yet another huge power hog.  The larger the Screen, the more power its going to use and this is something to keep in mind.  With OLED and other low power Screen technologies around the corner OEMS (Hardware Manufactures) should be able to improve battery life on devices. 

3. The Radio: The Radio (Wifi, CDMA, GPRS, EVDO, WiMAX, Bluetooth) causes major battery usage on Windows Mobile devices and its important to understand how quickly a device's battery can run down when these radio's are on.

• Cellular - GPRS, 1XRT, EDGE:  Most phones in the market have utilized this radio for the past few years  and when we look at a device we can use battery life with just the GPRS/1xRT radio as a base line if you want to compare it to other devices. 
• Cellular 3G - EVDO, HSDPA:   While the EVDO (CDMA) radio doesn't put a huge strain on a Device the HSDPA (GSM/UMTS) radio can considerably tax a devices battery.  Many Non-Windows Mobile manufactures haven't released devices that have HSDPA into the market place.  One of the speculated reasons is that HSDPA radios have an adverse effect on battery life and this is a major concern with current battery technology.  On the other hand with many Windows Mobile devices there are ways to turn off the high speed HSDPA radio.  I've blogged on how to do this on the Samsung Blackjack.  Disabling the HSDPA radio will improve battery life but it will also make you lose the functionality of the high speed radio.  This doesn't really effect the device if you are just using it for Activesync (Mail Sync) but if you are browsing the web or using your device as a modem for you PC then you'll want to make sure you don't disable the HSDPA Radio
• Bluetooth: Bluetooth is yet another Radio on the device that can affect battery performance.  While Bluetooth doesn't hit battery performance has heavily as perhaps an HSDPA Radio or a Wi-Fi connection it does impact how long the battery lasts. 
• Wi-Fi: The Wi-Fi Radio is perhaps the most power hungry radio found commonly on a Windows Mobile device.  For Customers running LOB applications with ruggedized devices the battery is normally big enough to handle all day usage of the WiFi Radio, however if we try to use the Wi-Fi radio on one of the consumer devices you're going to end up with battery life that will probably not meet a user's needs.
• Wi-Max: Wi-Max is something we've yet to find in any Mobile Device that are generally available however the battery consumption from a Wi-Max device is extremely high.  While I've yet to do side by  side comparisons, some have found that a Wi-Max radio can use more battery than a Wi-Fi radio.  Now Wi-Max is still in its very early stages so the Radio Battery consumption can be drastically improved.

4. The Hard Drive: While Few devices include a hard-drive, due to its moving parts a hard-drive consumes a considerable amount of power and can dramatically effect your battery life.

5. Battery Size / Type:  The battery size will directly impact how long the battery lasts.   Today with devices getting smaller the battery size also shrinks and its something to keep in mind when purchasing a device.

With all this said I often get the question:

"Well my old phone used to last for days but my new Windows Mobile Phone's Battery doesn't last that long."

If all you are using on your Windows Mobile device is the Cellular GPRS/EDGE radio then you should also expect a pretty long battery life.  I've used both the Blackjack and the HTC Dash with only GPRS/EDGE Radio enabled and I've gotten 2+ Days of battery life.  The Same device with 3G(HSDPA) had battery life that was considerably shorter.  When I left Wi-Fi on I got about half a day.   Now its important to keep in mind as you start turning on more and more radios it's going to impact your battery life.  Most non Windows Mobile devices don't have any of these advanced radios so their batteries last much longer.  Its key to keep this in mind when you compare and contrast the device you are purchasing.

I'm not advocating that you turn everything off on a device. What I am suggesting is that the more advanced your mobile device the higher you're battery usage;  in the end the enterprise or user will have the weigh the pro's of the the new advanced radios on a device with the battery performance.