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The Unipro user manual suggests
that after you inserted the AA batteries, for the first time
use you leave the Unipro docked in the cradle for approximately
12 hours with the AC plugged in and with the Unipro
turned on. A 12-hour time frame is recommended, though
3-4 hours will be sufficient in most cases. The purpose of
this procedure is to charge the internal Lithium Ion cell
fully. Lithium Ion cells hold charge very well. The Lithium
Ion cell in the Unipro serves the purpose of maintaining the
RAM data storage when the main AA batteries are exhausted.
Maintaining user data storage is obviously the most important
goal, therefore, the Lithium Ion cell charging function has
a high priority. The cell charges itself in whichever way
it can. If the external power is not available, then it charges
from the AA batteries and this is not a very efficient way
to charge the cell. Users may find that if they do not charge
the Lithium Ion cell in the beginning as recommended, they
will have quite a rough ride with the first couple of battery
changes. Then, the battery life will settle down and be more
predictable as it will be if the Lithium Ion cell was charged
correctly in the first place.
When the main AA batteries are
in very low power state, Windows CE low power warnings will
be displayed. Although Windows CE warning says that data will
be damaged, what really occurs in the Unipro is that it will
power-down to the power-save mode and refuse to re-start after
it determines that the main AA batteries are no longer sufficient.
The Lithium Ion cell takes over partially in supplementing
power. In this mode, the user data are safe for quite a long
time with the exhausted AA batteries still in the unit. When
the AA batteries are removed, fresh batteries must be inserted
as quickly as possible. Unipro claims 1 minute keep-alive
backup time as suggested by Microsoft for this design. It
actually lasts longer than that.
Even if Unipro appears to be on
all the time, the battery life would not be significantly
degraded, if the internal Lithium Ion cell is fully charged.
The reason that Unipro appears to be on at all time is because
the application buttons turn on the unit whenever they are
pressed. However, if the user does not utilize the activated
application, the unit powers down in 1 minute regardless of
the power-save configuration.
For heavy usage, the main AA batteries
last about 2-3 weeks without significant use of the back-light,
the voice recorder or the modem (about 1 modem call per day).
One set of AA batteries will last about 4-5 weeks if the Unipro
is used like a scheduler.
There is an interesting power race
behavior that is worth taking note of.
When the Lithium Ion cell power
is drained significantly, there is a power blind spot period
of one to two hours when there is enough power in the Lithium
Ion cell to keep the processor alive but not the memory. During
this period, if fresh AA batteries are installed, the Unipro
will not power-up. Fresh batteries will further charge the
Lithium Ion cell and prolong the power blind spot period.
This condition will not occur if
the Lithium Ion cell charging and battery maintenance procedure
is followed properly.
So far there are two ways you can
end up in the power blind spot state:
1. You install fresh batteries
into the Unipro for the first time and use the Unipro for
a short time, not long enough for the Lithium Ion cell to
be charged properly.
2. You leave weak AA batteries
in the Unipro for a long time after the Unipro refuses to
power-up following a series of low battery warnings.
If for any reason the Unipro refuses
to power-up due to the above power management problems, take
the AA batteries out and leave the Unipro alone for a couple
of hours or longer. The idea is for the Lithium Ion cell to
be completely discharged before re-starting the Unipro. Re-install
the batteries and charge the Unipro in the cradle with the
AC power on and the Unipro turned on for a few hours up to
12 hours.
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