charging battery while in a 2003 thunderbird

It doesn't sound like you are using a Battery Tender type product but want to use a full fledged charger. Most quality chargers will work with the battery connected in the car. Personally, I like to remove the cables and clean the terminals at this time. If the battery is running down, it may not be getting a good connection from the alternator. It is possible that this car being 11 years old, it is on its second battery and it may just be dying on you. Go to an auto parts house like Auto Zone, Advance Auto, etc and have it checked.

Hi have Same problem I parked the car for the winter battery went dead I recharge it and the alarm went off like crazy how are you we can fix that I turn the key on position then I’m going off I started up no problem but shown at unit off your alarm go crazy

I have same problem Anyone can help me on this