2000s Jaguar XJ8 Problem Resolution: NO START, WON'T CRANK

It's winter, and my 2003 Jaguar XJ8 (99k miles) has been reacting badly to the cold. First it did not properly auto unlock the other day at the gas station, locking me out. And then I came out the other morning to start it up and it was dead - no crank, no start. After spending some time charging the battery, thinking that either it was failing in the cold weather or there was some other electrical issue, I discovered the key I had been using - my spare key - had mysteriously stopped working. This is the first time I've ever had a failed security KEY be the reason a vehicle would not crank. The keys have embedded security features, but apparently this one has gone bad. Maybe other Jaguar owners will be helped seeing this. Luckily, I had two keys, so I can still drive it, but no fun knowing I'm down to just one key. WAYS YOU CAN SUPPORT THIS CHANNEL: ♠Stand in the Middle of the Street Naked Screaming "LONG LIVE THE GUITOLOGIST"! OR ♠Send an unwanted piece of gear or send a small tip via Paypal: [email protected] Thanks for your support! ♠STUFF I USE -5A Variac: http://amzn.to/2FNWthU -Fluke 87: http://amzn.to/2DwHjvr -Yotec 936 Soldering Station: http://bit.ly/2JqB1Vw -Sealody SSA51 soldering station: http://amzn.to/2DJTS7P -Black and Decker Heat Gun: http://amzn.to/2DWpDhr -Geekcreit® LCR-T4 Mega328 Transistor Tester http://bit.ly/2J9uLSA -HT02 Handheld Infrared Thermal Camera http://bit.ly/2LXfLoD -Solderless Breadboard: http://bit.ly/2stkVAq -Breadboard Jumper Wires: http://bit.ly/2JowaEh -Geekcreit® XR2206 Function Signal Generator DIY Kit http://bit.ly/2LYBvkb -Contact Cleaner: http://amzn.to/2FVitro -Deoxit Fader Cleaner: https://amzn.to/2LPwtsE ♠RECORDING -JVC Everio Camcorder http://amzn.to/2HF172t -Andonstar USB Microscope: https://bit.ly/2q8QIWz -Articulated Boom Arm with Cam Mount: https://amzn.to/2Hlo2AX -Shure Beta 87A https://amzn.to/2rNPnoW -EV 635A Omnidirectional Dynamic Mic https://amzn.to/2pR8HQT ♠BOOKS -RCA TUBE MANUAL http://amzn.to/2GOBVqS -DESIGN AND CONSTRUCTION OF TUBE AMPLIFIERS: http://amzn.to/2HSNMne -Designing Tube Preamps for Guitar and Bass: http://amzn.to/2DK5tmt ♠2006 FENDER AMERICAN STD TELECASTER PICKUPS -TV Jones Magnatron Neck: https://amzn.to/2q1zQjD -Seymour Duncan Vintage Stacked Bridge: https://amzn.to/2GyZjrK