[C] Date: 21 June 1999
From: Philip Wilk

The power brick that comes with the aero can plug directly into a 220 V
wall outlet like they have in Europe. No need for a transformer! To be 
sure, look at the voltage range listed on the bottom.

[C] Date: Mon, 14 Jun 1999 16:39:51 -0500
From: "Frank R. Borger_(FRB)" 

>Those Aero power bricks are totally 
>unshielded! No metal cage or even foil shield cage, nothing.  
>That's atypical of Compaq.  Must be cost cutting design.
>
>Somebody could do a pratical project transferring the power brick 
>guts and mount properly in metal box and hopefully see any 
>difference. 

Those bricks do pass EM radiation specs. If they pass TUV,
they are good units. However, the testing and specification
for near-field versus far-field is very different. 

The near field (the magnetic field from the transformer,) is what's
screwing up the floppy drive. It's also very hard to shield. (In the 
old days, you could easily screw up a 9-track tape just by laying
it down on the back of the case of a CDC or AMPEX 80mbyte drive
that was seeking a lot.)

Oh well, first we learn not to stick floppy disks to our fridge using
refrigerator magnets, and then....

;-}
Frank

[C] Date: Fri, 22 Jan 1999 17:08:05 -0800
From: Miker

> Buy a wall wart from Radio Shack.  I believe they have one that delivers
> 13-18V.  Anything in that range, with the same output as the compaq in
> amps, will suffice.

I take strong exception with this advice.
The Aero has a FET in series with the battery.  It turns on hard during
charging. When it's fully charged, the FET turns off completely.
So, while it's charging, the external power supply is connected directly
across the battery.  The current limit in the power brick reduces the
voltage to that of the battery and determines the charging current.

If you use ANY power brick other than the one supplied, you will get
the wrong current.  If it's just a little too much, you'll merely
overcharge the battery. If it's a little more too much, you'll explode
the battery eventually. If it's a lot too much, the FET will come out of
saturation and melt. See more on this below.

There are also problems with the power bricks,  They don't like to be
overloaded. In fact, many don't have any overload protection at all.  The
internal resistance of the transformer limits the current somewhat, but
causes overheating until the internal protection, fuse, thermal switch,
etc cuts out.  The rating printed on the brick has to do with UL and
safety laws.  You can NOT count on it to represent anything other than
the maximum RATED current of the supply.  RATED and ACTUAL are often NOT
the same.  If you stay within the ratings, the supply is not supposed to
catch fire.  If you exceed the ratings, the power supply is not
supposed to catch fire.  There is no guarantee that the load won't catch
fire.  The AERO is NOT a standard resistive load.

Many bricks with switching regulators have foldback current limit.  When
you stick this across a battery, you may get bizarre behavior.  Your hard
drive may be sorry this happened.

There are a lot of ways to design battery/charger systems.  The AERO 
system is particularly light weight, low cost and efficient, but it
depends completely on the characteristics of the AC power brick.

On a related thread, people have reported success connecting their aero
directly to a car battery. They have been lucky.  There's almost no
protection inside the aero for overvoltage spikes normally
found in an auto electrical system.  The internal battery will provide
some limiting while it's (over)charging, but as soon as the FET cuts off,
there ain't nothing to stop your starter spikes from trashing your
computer. The only reason this works at all is that the car battery
voltage with the engine off is low enough that you don't immediately
smoke the internal battery.  Running at 14.4V with the engine on is
definitely too much. Don't do it. MUCH MUCH safer to use a 12V to 110V
converter and the AC supply for the AERO.

miker