I would like to add a note about the F-type batteries which we have covered many times on this site. The very small battery, 5.5 pound Lithium-Ion battery in conjunction with the Tamdem Solenoid Starter, soul purpose is for starting your Jag. When your car is parked, no current is being pulled from this battery at all. These modern batteries can sit around for a considerable amount of time without any degradation. Now on the other hand, the larger battery on the left side of your vehicle is another story. There is always a current drain going on when your vehicle is parked. Lots of electronics still running even with your Jag locked (which also uses current). I would give this battery about a month before it starts dropping in voltage but we do have some good news.... your vehicle will start without it! Once running, it will charge up to full strength within a reasonable amount of time.....I would not worry about your batteries. Other makes (Mercedes & Bentley) have been using this double battery system for over 12 years so the customer will always be able to start the vehicle. The only real change is the Lithium-Ion/Lithium Hydride/Nickel Metal Hydride and the newest/Absorbent Glass Mat(AGM) are being installed. Hope this info puts your mind at ease......Pascha
