I’m about to go away for a few weeks and am concerned that when my XJ is parked up in the airports long stay car park that I may have a dead drained battery when I return.
Q. Can I easily isolate the power line from the engine compartment so that on my return I can use the ‘fob emergency Key’ to regain access and reconnect the power?

 

Langstraat, for what you are going to spend on getting things to do what you want, you may find it easier and cheaper to simply catch a cab to the airport and leave the car in the driveway on a battery tender. I am sure someone you know would be willing to drive you to the airport if a cab would be out of the question.

The best thing that I would say is if you look around, there are special 12V solar panels that you can put on your dash and plug into a cigarette lighter that has power all the time. That way, at night, the car runs off of the battery and during the day, the solar panel handles the loads of the car and tops off the battery. The big trick for this with our cars is most of the easy access points turn off once you lock the doors. So, a little bit of looking may be required. Might be one of those things that you would need to go directly to the fuse box.

 

Thermo,
I didn’t think a cost would be involved, just thought I could pull a fuse which would interrupt the battery circuit aftercentral locking had made it secure.
‘Close the bonnet and walk away.’

 

On the S-Type you could just disconnect the battery and close the boot (trunk) as it has an actual physical lock!

On the XJ? Does it have the lock? (I suspect not.)

 

I just started mine after two weeks being locked without a battery tender. The only message was low washer fluid. Started and ran just fine, I even listened for the timing chain noise or anything else. Everything was normal. You should be okay as long as you lock it and your battery has a good charge. I would think.

 

Because dead batteries are a common problem for cars in long-term airport parking lots, most lots have emergency vehicles for jump starts. Call your airport and confirm before you park.

 

Langstraat, keep in mind that the battery is in the trunk which requires power to open. So, if you disconnect the battery and then shut the trunk, you have essentially locked yourself away from the battery. Now, there is a procedure on this site that can get you around it, but it is probably more involved than you are looking to do in an airport parking lot.

Keep in mind that there are numerous computers inside the car. You would need to pull the fuse to each one of those computers. If you pull the megafuse (250 amp), this will be a one fuse to kill most of the power, but now you have disabled all the computers that allow you to unlock the car and therefore, because the megafuse is in the trunk, you are no better off than disconnecting the battery because of not having access to the trunk.

The only "fix" that I can think of for what you are desiring is to get a small say motorcycle battery that you can keep inside the car. This will be a 12VDC battery that will have sufficient power to get the car live again. What you would end up doing is with this battery inside the passenger area, you can park the car and disconnect the battery (killing the car electrically). At this point, you can close the trunk. When you return, you can manually unlock the door (do this one time in your driveway as the instructions threw me for a loop since it seems to show you doing something different than what is needed). From here, you can manually open the hood and grab the battery from inside the car. You can then access the fuse box in the engine bay and connect up to the megafuse there and the chassis to power up the car. From here, you can electrically open the trunk to reconnect the battery.

Keep in mind that if you do something like this, the car is going to loose all memory. So, you will end up having to reprogram your seats (as I recall) and reprogram the auto up/down feature of all the windows. The car may also run a little rough for the first 20 seconds or so as the ECU relearns a few things.

 

Many thanks for the reply’s . I’m aware that if the circuit to the battery is interrupted that to gain access on my return I’ll have to use the mechanical key within the fob to open the passenger door and then release the bonnet to get to the electrical panel. My post was to ask which of the fuses would ensure that the battery doesn’t discharge.
I wouldn’t have thought that a disconnected circuit to the battery would have caused any problems.

 

You can jump the car by using the emergency key and popping the hood. Jump taps are under the hood.

 

Why would you want to disable the alarm system, particularly while in long-term public parking, and leave it vulnerable? That's what will happrn, among other things, if you disconnect a battery cable. What am I missing?

 

My guess would be he's going away for more than two weeks. Maybe closer to months.

 

Yeah, about a month.

 

Before computers I could park my carburated car for a six month deployment and it would still start when I got back. That's not possible today. In your situation, I would try one of them solar chargers and see what happens. It might extend the charge just enough to start when you get back. If it doesn't, your no worse off. I'm sure your airports will have someone to jump the car for you. Just leave the owner's manual in the car so you can refresh your memory about how to do it safely. New cars are a lot more tricky than older ones.

 

It _should_ be fine for a month. That's if all is working (electronically/electrically).

It's the doubt that caused the question I think.

If the car is somewhere supposedly secure (airport car park maybe) then disconnecting the battery is probably "good enough".

(I'd have a spare battery or disconnect the one in the car.)

 

Yeah, my concern was the for the security system drawing the battery whilst I was away. I’m reasonably assured that the Airports secure car park will be sufficient and would rather be able to start her up whatever time I may return. I know what a pain it can be to return to a car with a flat battery after midnight and then wait for assistance to jump start it. After a long flight messing about and waiting in a cold car is’nt an ideal return home.

 

I just started mine .

 

The security system uses next to nothing.

It's the other things - if faulty - including any aftermarket or plugged in devices that are potential problems.