All,

Here is how to find the right AC adapter and how to build an external
battery back for the Zaurus, much cheaper than the Sharp-branded ones.

  DISCLAIMER: USE AT YOUR OWN RISK, IN CASE OF PROBLEM YOUR WARRANTY
  WILL BE VOID !!!

I found all I needed at Radio Shack:

(1) AC Adapter

I bought a generic AC adapter (1.5-12V 300mA). It comes with a series
of plugs, I selected the one that matches the Z connector, being careful
to select NEGATIVE tip.
I set it in the 7.5V position (which yields 8.5V). It is a good idea to
check voltage and parity with a voltmeter BEFORE connecting it to the
Zaurus for the first time. The reference is 273-1662, I paid $12.99
for it. It's a bit more than the Sharp one, but I saved a lot on
Shipping & Handling...

(2) Battery Pack & Charger

I bought a Ni-Cd Turbo Racing Battery Pack, specified as  7.2V, 1200mAh
capacity (meaning it could provide 300 mA for 4 hours, for example).
I measured the voltage: 8.2V. Remember that, as with AC adapters, the
voltage will drop a little when you connect a load (like a Zaurus) to
a power supply.

I bought the matching Battery Charger, which delivers 7.2V @ 100mA
(that's a 12-hour slow charge with the above battery).

Then I did some soldering. I first removed the "Tamiya" connectors from
the battery pack and the charger, and replaced them with phono jacks (aka
RCA or CINCH jacks). I placed the female on the battery side and the male
on the charger side, because this way the battery contacts are much less
exposed, and it can be dangerous to short a NiCd battery, while shorting
an AC adapter will at most toast it. I then made a short adapter cord to
connect the battery pack to the Zaurus (male phono jack on one end, and
connector matching the Zaurus on the other end --- for that one I
cannibalized an old AC adapter, but you can find matching ones at Radio
Shack).

This way I have a very clean and convenient solution: I can recharge my
battery pack overnight, and use it during the day for modem connections.
The modem I finally use is the Compaq SpeedPaq 144/P (supports cellular
direct connect). The back of the card states that it draws 220mA @ 5V,
which is a little more than 1W (1.1 W). With the 8.6Watt-hour pack
(7.2V x 1.2Ah), I can theoretically get nearly 8 hours of modem operation!

The reason I don't use the Battery Charger to power the Zaurus directly
is that it yields 100mA only, and the Zaurus plus the modem obviously need
more.
The reason I don't use the other AC adapter to charge the battery pack is
that it yields 300mA, which would give me a fast charge, but fast chargers
need to shut off automatically, otherwise NiCd batteries tend to overheat,
boil, vent, explode... which can be pretty messy...

References: 23-230, $19.99 for the battery pack; 23-241, $9.99 for the
Battery Charger.
That's a total of less than $30 (plus some change for the phono jacks).
To be compared to the $149 the Sharp battery pack kit retails for...

Oh, and for  those who wonder how big my battery pack is:
5 1/4 x 1 7/8 x 1 (inches). I don't know how big is the Sharp thing.

Files FIG1.GIF thru FIG4.GIF contain photographs of these accessories.

File WEDGE.GIF contains a drawing of what could be a product idea: a
wedge-shaped stand for the Zaurus, with an integrated battery. There
could be two versions of the product: one with just the battery, and
one with a battery and a modem. The battery would connect to the Zaurus
on the right side, and the modem through the 15-pin connector on the
left side. On the back of the stand there would be a connector for the
AC adapter, and an RJ-11 jack for the phone line.

Anybody interested in developping that product ???

--
Lionel Ancelet / June 19, 1996.

