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Sounds like a dead battery.

This is the text from Kia Canada regarding this problem on Sorento's

No.  FA0520070152 Language  English
Published  3/12/2007 Area  Canada
Model  Sorento(BL)(2005)
Gr./Sys./Comp   Automatic Transaxle   /   Automatic Transaxle
System   /   Automatic Transaxle Case
Subject  Sorento intermittent battery drain
Description This FAQ applies to 2004 - 2005 Sorento LX Vehicles with
an intermittent battery drain problem. This problem will most likely
be hard to re-create and detect using normal parasitic draw testing.

When the ignition is cycled to on, the Transfer Case Control Unit
(TCCU) enters a diagnostic state. If the ignition key is turned off
too quickly, the TCCU may become locked into the diagnostic state and
remain on, draining the battery overnight.

When presented with a 2005 Sorento LX that has a battery drain problem
and the system tests okay using the Micro 570 Tester as well as with
traditional parasitic draw testing, inspect the model number listed on
the TCCU.

The TCCU is located under the floor carpet on the passenger side of
the transmission tunnel. If the Borg Warner part number listed on the
unit is 44-50-000-073-D it should be replaced with an updated unit
available from the Kia Canada Parts Department. All replacement parts
have had this problem resolved.

Normal warranty policy and procedures apply.

Hope this helps