On the 600 Peak Amp Jump Starter I am seeing "FL" where the charged number appears?

The flashing "FL" indicates that the internal battery of the Peak Performance Jump Starter # PKC0AZ is fully charged and is ready to be used.

These "cheap jump starters" are little more than a Lead/Acid battery much like what is in your car. If they sit too long on the shelf of your local department store, without having a charge maintained, the cells in the battery will eventually collapse rendering them next to useless without quite a bit of work trickle charging them back to life. As the proud owner of several of these useless boat anchors I can advise you to save your money and just buy a really good vehicle battery (Interstate) that will be there when you need it, instead of wasting money on Wallymart specials that last 2 maybe 3 years. I have learned..... ;-) Take it back and get your money.

Maybe the rechargeable battery needs replacing. Go to a battery store and buy a replacement.

When the Jump-Starter is fully charged, the display will read FL. Disconnect the AC extension cord from the 110/120-volt AC outlet, and then disconnect it from the Jump-Starter AC charging plug. http://www.carid.com/images/peak/info/pdfs/pkc0j6-manual.pdf

Google for an owner's manual. I can't find anything on this jump starter, but first they need to be charged, usually by plugging into a wall socket for 12-24 hours. Then plug into the cigarette lighter for 10 min or so to give the car battery a boost charge.

should have an AC power cord to plug into wall outlet and to a charging plug on battery pack unit

FL Float Charging.

After searching the internet for a ph number for Peak power I finally found the web.
http://www.peakauto.com/contact/site.
phone 800-323-5400
If the part department doesn't have the answer ask to be switched to tech support.
They were able to provide me with the part numbers I need for new wall supply cord and an DC adapter for the car.
My jump starter is no longer made...