"occam" wrote in message ...

What exactly is the Acer recommendation - to take the battery out when
you are using the laptop with AC?

Yes, surprisingly.

(My Acer did not come with an operating manual - or any other
documentation - so I am interested to know where this is spelled out.)

You may be able to D/L a manual. This is from my manual for an Acer 3680:

Battery pack
The computer uses a battery pack that gives you long use between
charges.
Battery pack characteristics
The battery pack has the following characteristics:
.. Employs current battery technology standards.
.. Delivers a battery-low warning.
The battery is recharged whenever you connect the computer to the
AC adapter. Your computer supports charge-in-use, enabling you to
recharge the battery while you continue to operate the computer.
However, recharging with the computer turned off results in a
significantly faster charge time.
The battery will come in handy when you travel or during a power
failure. It is advisable to have an extra fully charged battery pack
available as backup. Contact your dealer for details on ordering a spare
battery pack.
Maximizing the battery's life
Like all other batteries, your computer's battery will degrade over
time. This means that the battery's performance will diminish with
time and use. To maximize your battery's life, you are advised to
adhere to the recommendations set out below.
Conditioning a new battery pack
Before you use a battery pack for the first time, there is a
"conditioning" process that you should follow:
1 Insert the new battery without turning the computer on.
2 Connect the AC adapter and fully charge the battery.
3 Disconnect the AC adapter.
4 Turn on the computer and operate using battery power.
5 Fully deplete the battery until the battery-low warning appears.
6 Reconnect the AC adapter and fully charge the battery again.

Follow these steps again until the battery has been charged and
discharged three times.
Use this conditioning process for all new batteries, or if a battery hasn't
been used for a long time. If the computer is to be stored for more
than two weeks, you are advised to remove the battery pack from the
unit.
Warning: Do not expose battery packs to temperatures below 0°C
(32°F) or above 45°C (113°F). Extreme temperatures may adversely
affect the battery pack.
By following the battery conditioning process you condition your
battery to accept the maximum possible charge. Failure to follow this
procedure will prevent you from obtaining the maximum battery
charge, and will also shorten the effective lifespan of the battery.
In addition, the useful lifespan of the battery is adversely affected by
the following usage patterns:
.. Using the computer on constant AC power with the battery
inserted. If you want to use constant AC power, you are advised to
remove the battery pack after it is fully charged.
.. Not discharging and recharging the battery to its extremes, as
described above.
.. Frequent use; the more you use the battery, the faster it will reach
the end of its effective life. A standard computer battery has a life
span of about 300 charges.
Installing and removing the battery pack
Important! Before removing the battery from the unit, connect
the AC adapter if you want to continue using your computer.
Otherwise, turn off the computer first.
To install a battery pack:
1 Align the battery with the open battery bay; make sure that the
end with the contacts will enter first, and that the top surface of
the battery is facing up.
2 Slide the battery into the battery bay and gently push until the
battery locks in place.

To remove a battery pack:
1 Slide the battery release latch to release the battery.
2 Pull the battery from the battery bay.
Charging the battery
To charge the battery, first make sure that it is correctly installed in the
battery bay. Plug the AC adapter into the computer, and connect to a
mains power outlet. You can continue to operate your computer on AC
power while your battery is charging. However, charging the battery
with the computer turned off results in a significantly faster charge
time.
Note: You are advised to charge the battery before retiring for
the day. Charging the battery overnight before traveling enables
you to start the next day with a fully charged battery.
Checking the battery level
The Windows power meter indicates the current battery level. Rest the
cursor over the battery/power icon on the taskbar to see the battery's
present charge level.
Optimising battery life
Optimizing battery life helps you get the most out of battery
operation, prolonging the charge/recharge cycle and improving
recharging efficiency. You are advised to follow the suggestions set
out below:
.. Purchase an extra battery pack.
.. Use AC power whenever possible, reserving battery for on-the-go
use.
.. Eject a PC Card if it is not being used, as it will continue to draw
power (for selected model).
.. Store the battery pack in a cool, dry place. The recommended
temperature is 10°C to 30°C. Higher temperatures cause the
battery to self-discharge faster.
.. Excessive recharging decreases the battery life.
.. Look after your AC adapter and battery.