When I saw that there was a battery extender out for my Zaurus and Axim I decided I had to buy one and give it a try. My hopes were that it would greatly increase the Wardriving abilities of my Zaurus 5500, and to cut to the chase it certainly does. Basically, the way these battery extenders work is by filling them up with rechargeable AA batteries and hooking the extender to the external power input of your PDA. The device is not complicated and you might be able to make one yourself with a few parts from an electronics store.

        I did some surfing around on Froogle for the cheapest price and I ended up buying it from from Semons & Co. Inc ( http://store.yahoo.com/semsons-inc/pdabatexpocp.html ) for $6.99 plus shipping and handling. When it was first shipped someone or something had opened the envelope it came in and the 1600 mAH Capacity "AA" NiMH batteries I ordered with the extender  had fallen out, but a quick email to Semons and they resent the batteries. Semons service was good, I can recommend them and would buy from them again.

        Once all of the stuff I ordered got to me I went about testing the equipment to see if the extender increased the battery life significantly. Here is a rough timeline of my tests.

10:39 am - Plugged the extender into my fully charged Zaurus and started to run Kismet 3.1 using my Ambicom WL1100C-CF 802.11b Wi-Fi card. The back light was set to half of max brightness and to turn off after about 20 sec of not being used. The backlight would go on whenever I tapped the screen to check the status.

12:08 pm - Turned the extender and the Zaurus off and went to see Jersey Girl.

3:00 pm - Turned the extender and the Zaurus back on and started running Kismet again, I had to reset the Zaurus a few times because I kept filling up my root partition with data files from Kismet and other apps I was running.

5:00 pm - I notice the internal battery reading was at about 75%. The battery monitor on the Zaurus does not always give you an "on the spot" reading, if fluctuates a lot. I though maybe the AA batteries in the extender had been used enough to where they had become a load themselves, so I unhooked the extender from the Zaurus and the internal battery took over. The reading of the internal battery jumped up at this point to 100%.

7:00 pm - The internal battery got down to about 12% so I hooked the extender back up. It seems that the Zaurus 5500 can run for about 2hrs on the internal battery while using a Wi-Fi card in RF monitoring mode. I got my Zaurus used so your mileage may vary.

9:00 pm - I got bored with the test, so I set the back light to full brightness and set it to never turn off. The battery reading actually jumped up! As I inferred before, don't trust what the battery reading says.

9:15 pm - If memory servers, I looked down at the Zaurus at 9:14 pm and it was still on, but when I looked back at 9:16 pm it was off. At this point I had to take it upstairs and put it on a charger.

        Summary: The extender let me take the battery life from 2 hours to about 7 hours and 45 minutes. That's one hell of a wardrive/warwalk. If you want to use the Zaurus as a mobile hack tool get an extender.