Any advise on a 2008 jag XJ with severe battery drain after being stored for a 5 month period. It has a brand new batter and is still draining in a day.

Check battery. May be the battery is shorted. To drain a H8 series requires a hard load. Something should heat up.

Try disconnecting the negative battery terminal, when you park it.
If the battery stays up, good chance you have an open diode in your alternator.
Drawing constant current, which can take it down over night.

Battery on charge tonight to try tomorrow, thanks for advice so far

Was the battery new before or after the storage period?

I'd say leaving a modern car with a lot of modern electronics unattended for five months is asking for trouble. For that length of time you really should disconnect the battery.

From other people's posts here (and the UK based X350 forum) over a few years now I have the general impression that anything beyond four to six weeks causes trouble.

The battery was new after storage.

Just to note the car was stored for 5 months but was periodically started and ran. (stored in an air chamber)The last attempt to start the car in storage was met by a complete battery failure, no ignition lights, nothing at all, hence why I bought a new battery whereupon the car started fine but after being left for two days to set up mot, tax etc the car was stone dead again!, so that is where we are just now.

That may mean you have a drain. You can either follow threads about finding drains or put it on a ctek-type device.

Have you tried the negative disconnect yet?

Have seen this happen before, the alternator charges the battery fine.

An open diode, a one way valve, so to speak, has these symptoms.

Weather here in south west Scotland terrible ( rain, sleet and hailstones) so waiting for a day where weather is reasonable to start messing around with electrics of car. Battery sitting fully charged on ctek charger.

Ok so went out to start to look at what is draining the battery and the car would not start or even turn over. Battery fully charged with ctek charger. Noticed alarm led flashing continuously!! Any ideas?

I don't know so I have to guess.

I would put an ammeter on the battery line if I suspected untoward drain. But a high drain would not explain taking the battery off charger and not being able to start.

You might have a dud battery even though you say it is new. Easily solved by some other battery or jump starter.

The car has been left for a long time and now battery problems. The chances that it's caused by "excessive battery drain", whilst possible, would mean that it developed some other fault whilst stored. Unlikely. Whereas a dud battery or seized engine seems more likely to me.

How would you know unless you use some other starting means? (such as yet another battery or jump starter) It's always possible that the Starter Motor packed up with unfortunate timing. Best I can think of, Chris (My Honda Elysion packed up last year with broadly these characteristics. It was the starter motor, the battery was fine, and you have given no indication of checking battery voltage/condition etc just saying "new" doesn't cut it)
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I know this will go down like a lead balloon on a self-help forum, but when my Honda Elysion packed up (wouldn't start) I called out the AA and then a tow-truck. And I was correct to do so, but only as it turned out (starter motor). The probability of the starter motor packing up at an inconvenient time is small, but then the universe is full of amazing coincidences.
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You haven't measured a high battery drain. Unless you do, it is merely a supposition. And it wouldn't explain an immediate transfer from Charger to Start. If you want to DIY on battery drain, at least buy a multimeter?

Thanks for your reply. I have probably not given enough detail to the situation so here goes.

Car stored over winter but periodically started and ran, last attempt to start and run for a while found battery completely dead, no central locking, dash lights, interior lights etc, jump start failed so purchased new battery (from jaguar) and car started first turn. Car used for the day and then left for a week. Went to start again and flat again, as in no dash lights, no central locking etc. New battery taken out and trickle charged (auto electric garage) and returned to car. Went to start car and dash lights etc and power to everything but refused to crank. Eventually with trying several times and locking, unlocking car several times it started. Car used daily with no issues, left for two days and battery flat again. Battery charged again and put in again and power to everything but no crank. Noticed alarm led flashing constantly now. I am not massively electrically minded but father in law is an electrical engineer and has all the meters etc. To measure current, voltage etc. But I am now thinking the immobiliser/ alarm is not allowing the car to start.

Hi All, need your help. I have a 2006 XJ VDP. I bought a brand new battery 2 months ago and lately suspect I have a battery drain. I am going to do the ole ' one fuse check at a time' routine with the voltmeter and all but I need to know is where the trunk light switch is and if there is a engine hood light switch as well from the days when I had a 2009 VDP which I believe had a engine hood light. I have read that you need to bypass those items as well with a paper clip or such as well as clicking the door latch to 'fool' the system the door is closed so I can do the cabin fuse box check too. I also believe I saw in the threads somewhere that the standing voltage on a good system is about 30ma, true?

Thank you in advance

The trunk light can be switched off with the trunk open by pressing the latch closed with your fingers. Just remember to open the latch with the button before you slam the trunk!

I measured ~36mA standby current draw, this with car locked and the measurement was actually the trickle charge current to maintain 13.6v, of course once the battery was settled into fully charged.
(The charge current was averaged over 24hrs. Since various computers are said to wake up, who knows what it is temporarily)

There is no under hood light - this is for the thread hijacker - no offence, lol. There is an "Open Bonnet" switch in the left latch, and they occasionally fail disallowing the alarm to be set and falsely indicating an open bonnet. THAT switch can be jumped with a small piece of wire - or rather the wire plug gets jumped.

Thank you Gentleman! Time to get to work.