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HP iPAQ HX4700 PDA Backup Battery Replacement Guide
A pictures illustrated instruction manual for replacing the NiMH backup battery in an HP iPAQ HX4700 / HX4705 PDA.

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HP iPAQ HX4700 PDA
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3.7V 1800mAh Li-Ion Battery

 
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Allen Key Hex Wrench Set

When I first bought my shiny new Hewlett Packard iPAQ HX4700 (a.k.a. HX-4705) personal digital assistant it was going to be primarily used for GPS in-car navigation.

I thought I would never need a spare battery since I could always just use the travel wall charger or 12v car charger that I had ordered from Box Wave.

Then I started exploring the other entertainment possibilities of my PDA including listening to MP3's, watching movies, surfing the web, and playing video games.

After the first long airplane flight with multiple layovers, I decided to buy an extra generic Chinese 3.7V 1800mah battery on eBay.

What I didn't know then was that changing the main battery with both the SD and CF card still in the PDA was severely straining the tiny rechargeable NiMH backup battery inside the HX4700.

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Back Cover Removed
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Varta V6 HR Ni-MH Button
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Tweezers To Pry Out Battery
The small 1.2 Volt 6 mAh Ni-MH Varta V6 HR button cell backup battery was only designed to maintain the iPAQ's main internal built-in memory during loss of primary battery power, and not also the expansion Secure Digital and Compact Flash cards. Maybe I missed it when I read the HX4700's owner's manual but I'm sure it must mention that you should remove all the add-on memory cards when swapping main batteries. The backup battery held up under the abuse for about a year with various road trips and air travel. Over time I had to switch out the main battery packs with increasing speed or risk an inconvenient hard reset, initial setup process, and backup file restore procedure. Supposedly the backup cell should last at least a few hours but I was lucky to get a couple of minutes when I first started using a 2nd main battery.
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Back Up Battery Location
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Compared To Penny & SD Card
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Back Of Rechargeable Cell
To access the HX4700 / HX4705 backup battery you'll need to remove the 4 Torx screws on the back of the PDA that require a T-05 or T-06 size Torx tool. I was able to take out the screws by using a small allen key hex wrench. You might also have luck with a small flat head screwdriver. Remove the main battery, then lay the iPAQ down so that you can read the FCC & Hewlett Packard information on the label. Then once the four screws are out, gently lift the case on the left hand side first. Take care not to lose the little black plastic piece at the top right because it is a separate part. Don't use much force, the back of the case should come off fairly easily with some wiggling. Check picture # 4 on this page to see the location of the back up battery button cell. You'll probably spot it right away. I used some fine tipped tweezers to pull the cell out. Be careful not to scratch or gouge the circuit board that is underneath the backup battery holder.
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1.2V 6 mAh Germany
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Lil' Sync AA USB Charger
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Pocket PC Techs Product
I included a few pictures of the German made micro battery next to a USA penny and an SD memory card to give you an idea of it's extremely small size (actual dimensions are 6.8mm diameter, 2.15mm height, with a weight of .28 grams). According to the Varta website, the cell has an expected trickle charge "long lifetime" of 5 years with over >500 drain/recharge cycles. Besides Nickel Metal Hydride batteries, Varta also manufactures other cells such as Lithium Ion buttons, the Lithium Polymer "PoliFlex", Zinc Air, Silver Oxide, Oxygen Sensor, Hydrogen Generating, and Lithium Smart Card Power. As I'm sure you can deduce, I was very impressed with their interesting product line and spent about fifteen minutes reading the various detailed battery specification pages.



 

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When Lit VRC is Disabled
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Female USB Plug
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Made In China
After searching the internet for "Varta V6 HR", I realized that I wouldn't be able to run down to Wal-Mart, or Radio Shack to buy a new one. Finally, I found a BrightHand message board thread that recommended Pocket PC Techs as a good online source for PDA & Smartphone parts. I bought the new battery for $15.00 and also added a "Lil' Sync" USB AA Battery Adapter charger for $19.99. I figured that if my iPAQ's backup/primary battery selector rocker switch was broken, as one Bright Hand forum poster suggested, I could just keep the main battery permanently in the PDA, charge it with the AA adapter while flying and toss the generic eBay "Made In China" batt into the back of a drawer to be forgotten.
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Voltage Reduction Circuitry
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New Backup Battery $15.00
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New Varta V6 HR Installed
The new backup battery popped in easily so I replaced the back cover and the main battery pack. When I first turned the HX4700 back on, I of course had to go through the hard reset initial setup and backup restore process. I checked the power status page and the new backup cell was at 0%. I put the PDA back into the cradle and left it alone for a few hours and then when I checked again the status was at 100% for both batteries. The real test was when I pulled out the SD/CF memory cards and the main battery pack for a few minutes. When I put the main battery back in, the PDA started up like a soft reset with all my programs still intact.
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Backup Battery Recharging
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AA NiMH Powerizer
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Backup Battery Fully Charged
After fixing this problem I thought about upgrading to the newer Windows Mobile 5 or 6 (WM5 / WM6) operating systems from the WM 2003 SE (Second Edition) that shipped with the 4700/4705. But since I only use the PDA for iGuidance 3.0 GPS navigation, Gmail Email, and TCPMP (The Core Pocket Media Player) to listen to mp3's and watch movies, I figured that why mess with what works. Everything that I use in WM2003SE runs very quickly on the HX4700's 624Mhz Intel Bulvedere processor and 192 mb of memory (128 ROM, 64 SDRAM). I paid $460 for this iPAQ back in August of 2005 and it has been worth every penny. For more check out my HP HX4700 Review & GPS Navigation page or the Lil' Sync USB Charger Review.
 
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