Thx for the reply.
Very interesting. I accept your explanations, you're right on voltage vs current for charging and probably on AGM requirements and ECM (I was not aware).
However...

When I go to the Varta site and look for what should I put on a X350 4.2 SC, they offer Silver Dynamic and Blue Dynamic models (which, I understand, are silver calcium technology unless I am wrong) but also Silver Dynamic AGM, which is AGM technology, which should not be ideal wrt ECM:
Search | VARTA

In Europe, X350s were delivered with Varta batteries, so we may guess Varta knows what a X350 4.2 SC ECM may accept. Or not?

 

I can assure you that both Silver Dynamic and Blue Dynamic are Silver Calcium batteries. That information comes from Varta and Johnson Controls directly. You are certainly safe with those, and are what Jaguar specifies for the X350, X355, X356 and X358 models. Personally I would steer clear of AGM for these models.

 

My first post, and I've already learned so much. This site and you guys a re great.

 

I had a similar problem with my X350 XJR and it was the battery. Any dip in power and you get all sorts of problems. charge it and I'm sure you'll be up and running.

 

I charged the battery, it would not hold a charge. Just bought another and everything is working fine.