I have an xjl , 2016 model. Every time I get into my car a message appears “ low battery, start your engine “?
I contacted a local guy who advised me to replace the battery for my key chain. Which I did. The message didn’t appear for couple of days but it is back again.
any advise?

 

Wrong battery. The message is warning about the main battery in the trunk. You need to get a new one.