Gentlemen, did the question of finding a source for the auxiliary battery ever get resolved? I have 60 months on both batteries in my 2014 XJ and it's time to replace them. The big one is readily available in a good AGM brand. I'd love to get the little one from someplace other than the dealer. Is there a source identified for the little one in an AGM?

 

It's an Exide EK151, search the interwebz and Fleabay and you might find a seller.
Or else take the easy and sensible option and just disconnect the pesky and useless thing, see these two threads: https://www.jaguarforums.com/forum/f...ighlight=exide
https://www.jaguarforums.com/forum/x...ighlight=exide

 

I happened to have just replaced this little battery as well. My old one was replaced in 2016. However I kept getting low battery warning recently with no reasons, the battery guy tested voltage on both and said the little one was at low voltage (not sure if it meant dying), but he did not sell this secondary battery. Anyway, I have assess to Chinese OEM parts so I just replaced it. Just cost me less than USD$70 and it's Genuine. Maybe you could find it on Alibaba.

 

Thank you, gentlemen, I have discovered several retail shops supplying the Exide EK-151 in the UK. However, the issue is how do I locate one that will deliver to the US.
Does anyone have a US outlet or is this battery locked out of the US by Jaguar?

 

Gentlemen, thank you for the advice. I have decided to let the pesky auxiliary battery die & disconnect it. This will happily eliminate the nuisance safety compromising stop-start feature as well.
FYI, the Jag dealer quoted $565 for the main battery and $481 for the auxiliary battery installed plus tax.
I paid the local battery warehouse $222 incl. tax. for the exact AGM main battery replacement installed.

 

If your primary battery isn't sufficiently charged, stop-start won't work even if the auxiliary battery is fully charged. That can happen if you primarily make short trips around town, with only occasional highway driving. Like I do.

How do I know this? From my Service Adviser after paying dearly for a new auxiliary battery and a few days later stop-start didn't work. I thought they sold me a defective battery, but they did not. Problem solved by leaving my CTEK MUS4.3 battery maintainer hooked up overnight to my primary battery. Note that because the primary battery is AGM, the CTEK must be set to Winter Mode - with the snowflake icon - for the proper charging profile.