Hi. The answer to my query may be buried here somewhere but can’t find it.

Essentially i I had to call out breakdown assistance the other day as the car wouldn’t turn over. Made all the clicking but wouldn’t turn over. Mechanic who can our suggested jumped the battery and it turned over. Got a new battery yesterday, drove it fine and then parked it up for about 10 hours. When I tried to start it same thing again but it eventually turned over. Went out later and no go and same again today. Any suggestions? I have attached a photo of the battery and one stray lead that I have no idea about.

Battery with stray lead!!

 

Well we need to know what car you have but at least I can answer about that stray white lead.
The reason is with all the battery problems on the XJ they updated/upgraded the BMS (Battery Monitor System) I think in 2013.

That white wire is actually used when the factory ships the car to your local dealer. We think it's some kind of battery disconnect so the battery does not go dead in shipping. The dealer as part of the pre-sale inspection is suppose to hide and tie that back out of sight.

So just ignore it but be aware you do not want that to ground out on anything!

Is the car going to sleep? Maybe try locking it in the garage.
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Hi thanks for coming back to me. It’s a 2011 3.0 xjl. Since posting the original message I actually got the battery guys to pop back out to check the battery they installed. Their puzzlement was that it was dropping from 4.6v when installed to 4.3v within a few minutes as if something was draining it. They replaced the battery again but same issue with voltage. No electronics apart from the boot being open. Got it started but have no faith in the issue not reoccurring. Anyone else come across this before?

 

Is that a typo?
4.6V is WAY low? Maybe 12.6V?

Yes it points to a current drain which most likely is just the car not turning off or going to sleep. But that is very quick and major drain so you might have a larger problem.
You might need a trip to a dealer or a good aftermarket electrical repair shop.

I don't know how DIY you are?
But you can test for current drain yourself. Where do you store your car keys? All FOBS should be stored away from the car if possible.
Do you leave anything plugged in? BT or OBD tester, radar detector or something like that? Has a trailer hitch been added to the car?
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Be sure the Battery is an absorbed glass-mat (AGM) battery, as non AGM batteries will exhibit the issues you are having. Also 900cca is better, to.

 

Sorry typo with voltage,missing a 1. As for battery it’s a 019 as the car doesn’t have stop start functionality.