I hate to mention it but the 2009 owners manual also says under Battery Charging:

"The battery must be disconnected and removed from the vehicle before charging. Failure to do so could result in damage to the vehicle's electrical system."

So you are not following their instructions either

It also say in that section:

"Always follow the instructions supplied with the battery charger. Failure to do so may result in damage to the battery."

So I guess we are all OK then as we are following their recommendations for connecting the leads

 

I have a sealed AGM battery. Does this reduce the risk of explosion?

 

I'm not an expert and don't know for sure, but I just did a quick Google search "are agm batteries vented". See Sealed Batteries Still Need Venting | boats.com Blog The author states:It appears that so-called "sealed" batteries aren't really completely sealed.

 

Not so fast... We are talking about two different sections of the Owner's Handbook. They are separate, just like apples/oranges... or, in this instance... Using Booster Cables/Charging the Battery.

Note that the Handbook is divided into chapters and sections. Under the Vehicle Battery Chapter the section headings are in BOLD CAPS, as follows:
VEHICLE BATTERY
BATTERY WARNING SYMBOLS
BATTERY CARE
USING BOOSTER CABLES
CHARGING THE VEHICLE BATTERY
CHANGING THE VEHICLE BATTERY
EFFECTS OF BATTERY DISCONNECTION

Your quotes are from page 189 of the 2009 Owner's Handbook (USA) under the section titled "CHARGING THE VEHICLE BATTERY". Charging the battery is different from maintaining the battery. Jaguar recommends removing the battery before charging it because a quick charge could damage electrical system components and cause the electrolyte to boil and produce hydrogen gas, which is an explosion hazard in the confines of the battery compartment.

I am referring to pages 187 and 188 of the Handbook under the section titled "USING BOOSTER CABLES". Removal of the battery is not required when using booster cables, and Jaguar recommends connecting to the remote battery terminals. Yes, we are charging the battery, but is is not a quick charge; our smartchargers apply a trickle charge.

Here's the link to that Handbook. JJM 10 02 30 901 - XK - OWNER’S HANDBOOK | TOPIx On the left side of the page click on Vehicle Battery. That will take you to page 187. Read those two sections as being separate and you will see the differences between using booster cables (for a weak battery) and charging the battery (for a dead battery). Unfortunately, the Handbook is ambiguous and could have been written more clearly.

Notwithstanding the above, as I said previously - your car, your choice.

 

Yup, I appreciate that and, as shown in the picture in the manual, that booster section is very clearly dedicated to attaching a donor battery to the car which is not what we are talking about. It even explains that in that section. You seem to be happy to interpret it differently but then are unwavering about not attaching any lead directly to the battery. The 2014 UK manual calls them jump leads in that section, not booster cables, so there should be no confusion in terminology.

If you insist on following the manual to the letter then you should disconnect the battery as there is no mention of any other sort of 'booster' in that section. I think we are all sensible though and realise that isn't necessary.

The workshop manual notes "Although also fitted to coupe vehicles, the remote jump start terminal has been specifically designed to allow a convertible vehicle to be jump started if a drained battery is experienced when the top is in the stowed condition"

Although it is handier to use for those of us with coupes that kind of implies they wouldn't have bothered fitting it if it wasn't for the convertible.

Lets therefore have a look at the XF owners manual:

"1. Connect one end of the positive booster cable to the positive terminal on the donor vehicle's battery.

2. Connect the other end of the positive booster cable to the positive terminal on the disabled vehicle's battery.

3. Connect one end of the negative booster cable to the earth point of the donor vehicle that is recommended for jump starting by
the manufacturer.

4. Connect the other end of the negative booster cable to a suitable earth point on the disabled vehicle. The earth point should be at least 0.5 metres (20 inches) away from the battery and as far as possible from any fuel or brake pipes."

That has been standard practice with jump leads since forever but for some reason no one will die and there won't be an explosion on those cars when you attach the positive booster cable directly to the battery but there will be on an XK?

The XF manual also mentions not connecting 12 volt equipment directly to the battery and like the XK manual actually gives an example of what they mean:

"Do not connect any 12 volt equipment (e.g. a 12 volt inspection lamp), directly to the battery terminals."

An inspection lamp without a switch is likely to cause a spark as you connect it, an unplugged remote battery charger lead is not.

So I still think that if you have a 5.0L car with the BMS the earth lead should ideally be connected remotely so it doesn't get confused but there is no reason why you shouldn't attach the positive cable directly to the battery which is what the instructions that come with the Jaguar supplied charger say.

 

Fascinating. I had never thought of what might happen if my battery died with the top down. So it has nothing to do with the possibility of a battery explosion? Who woulda thunkit??