So my wife's battery was dead well it was showing 9volts after sitting for 17 days or so. The idiot that Jaguar Roadside sent out wasn't much help as he showed up with a jump box with 1/2 a charge in it at 12.3 volts. I trickle charged it and then was able to jump it from the XJR. Since it is going on 5 years old I replaced it today but I'm a little confused as to what the second small motorcycle battery is and what it does sitting in front of the type 93 battery. Should I also think about replacing it?

Thanks for any input!

 

The second/small battery is for the stop/start ("eco") system.
The main battery is still used to power the starter motor, the secondary battery powers the ancillaries when the engine has been shut down by the stop/start system.

 

Gotcha, just curious about it. Couldn't figure out what it was there for. Thanks!