After a 20/30 minute drive 'TEST' was reading a 11.8v.
Is this normal or does it mean is time to change the Battery?

The car starts everytime so would this change impact in anyway the fuel consumption or any other thing?

Cheers

 

Was the battery fully charged before making this test? if it was, you may have another problem, with the charging system, like maybe the alternator......be cool.....Mike

 

I´m not sure since I had just been taken this short drives 2 times per day and sometime 1.

Which I don´t think could be enough for the battery to fully charge.
Regarding the alternator won´t it influence the working ability of the other components if it wouldn´t working properly?

Thank you

 

How did you perform the above test?

Directly measured on the battery terminals?

Engine running?

 

The TEST is a scan feature of Jaguar Message Center on the dashboard.
Was done as I said after the car stopped and runed 30 min.

Cheers

 

John, the question is whether the voltage measurement through the instrument cluster was done with the engine running or not. If this voltage was taken with the engine running, then this would indicate that the alternator is not functioning like it should. If the voltage was taken with the engine off, then this would indicate that the battery is having issues.

A 30 minute run should have brought the battery up to a near full charge. Now, I am assuming that you are able to start the car using the battery. If so, this would point more to a bad battery cable than a battery or alternator. This is where I would say to take the car for a drive and make sure to keep the dash fan on high and the seat heaters on. THis will put a large electrical draw on the car. After a 15 minute drive, open the hood and put your hand near the battery terminals (engine may or may not be running, doesn't matter). Is one battery terminal very hot or are they both about the same temp? They may be warm, but should not be hot (ie, worried about burning your skin). If they are hot, then you have a bad battery cable. Replace that first and then see what you have.