On most toughbooks please follow these instructions in order:
Step 1: Please Un-Plug AC Adapter (External Power Supply).
Step 2: Please Remove Internal Toughbook Battery Pack
(In some cases, you must release the latch located on the underside of the Toughbook).
Step 3: Do not put back the internal battery but plug back in the AC Adapter.
Step 4: Turn on the power (ie. start-up the Toughbook with the power button).
(In most cases the Toughbook will turn back on without the internal battery pack).
Step 5: Once the Toughbook is powered back on, do a complete shutdown of Windows.
Step 6: Put back the internal battery pack.
That is it. Your Toughbook should now work as normal.
Good Luck and Regards from:
Richard, Montreal Based Panasonic Canada Authorized Toughbook Dealer since 1989.