HP iPAQ Backup Battery Replacement Guide - HX4700/4705

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I just recently had to deal with the inconvenience of a worn out
backup battery in my HP iPAQ HX4700 PDA. Every time I would swap the
main battery back out for my 2nd one on a long plane flight, I'd have
to go through the hard reset process, initial setup, and backup file

I took pictures of the process and wrote up a quick guide to help any
of you who want to replace the backup cell in your iPAQ.

Here's the guide -

I hope some of you find it useful. My PDA is now healthy again. :)

Paul Michaels
Ft. Lauderdale, FL

Re: HP iPAQ Backup Battery Replacement Guide - HX4700/4705

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The glaring error in the guide is in these two paragraphs:

"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.

"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."

The error is that the backup battery does *not* supply any power at all to
either the SD or CF cards as these are based on FLASH technology that
requires no power to maintian their contents.  Further, the backup battery
will (or should) maintain the contents of the internal RAM for considerably
longer than the time required to change the main battery and is not in fact
under any strain at all.

Re: HP iPAQ Backup Battery Replacement Guide - HX4700/4705

I'm not so sure that is true for my specific model, the HP iPAQ
HX4700 / HX4705.

I just did some testing. With the 2gb SD card and 2gb CF still in the
PDA I pulled off the main battery and let it sit for 30 seconds.
(Approximately timed by my watch.)

Upon re-installing the main battery and after the soft reset, I got a
warning that the backup battery was low. I checked it and it was at
only 25%. I'm guessing that a few seconds longer would have meant a
hard reset.

I'm going to wait for the backup battery to recharge to 100% and then
repeat the experiment with both memory cards removed and my cell
phone's stopwatch keeping track of the time.

With both the cards out, after 30 seconds, the backup battery was at
50%. So I guess that's an improvement, but I'd still want to be very
quick when switching out the main battery for the 2nd generic one I

Maybe we have different PDA's or maybe something is wrong with mine.
Either way, I'm thankful that with this new backup battery installed I
do have at least 30 seconds to switch main battery packs.

I've found since then that I prefer not having to mess with the main
battery pack at all. The "Lil' Sync" USB charger AA battery adapter is
an easier way to keep my battery charged up since I already have a few
sets of high capacity NiMH AA cells for a camera.

Here's some pictures of the Lil' Sync -

In case I didn't mention it earlier, and it makes a difference, my PDA
is still running the original WM 2003 SE.


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Re: HP iPAQ Backup Battery Replacement Guide - HX4700/4705

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We have several people in the office who own various vintages of iPAQ
(though not your specific model).  I do not know of anyone who whould not
feel comfortable leaving the main battery out for considerably longer than
30 seconds.  I have just tried mine for 5 minutes and the backup battery
still shows 100% charge (in fact I have never seen it show anything else -
except when the iPAQ was new, and even then the battery wasn't anywhere near

There is no reason to supply backup power to any form of FLASH card, and it
is hard to understand why their presence affects your backup battery so
much.  Most forms of RAM memory can be maintaind by a small coin battery for
several years, so I'm not sure what HP are maintaining with yours.

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