When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have the usual issues of battery drain on my 2003 4.2 XKR. I don't have the option of hooking the car up to a charger/conditioner so I've been looking isolator switches, preferably remote control ones. I came across this one and it seems to be what I'm looking for.
I wouldn't use one of those myself as the relay in it is likely to melt at some point, either leaving you with a car that won't start, or worse, a disconnected battery while the engine is running.
If you really want to disconnect the battery, I think a good quality manual isolator like they use on boats would be the best way to do it.
Actually, thinking about this some more, you could add the isolator to the smaller of the two fuses at the High Power Protection module, rather than at the battery. This would leave the starter/charging circuit intact, only isolating the rest of the car. You'd need to check the wiring diagram for your car to see what that would do, but at least the Chinese relay would only be carry a few 10s of amps maximum rather than 100+ amps and most importantly, when it inevitably fails, the battery and charging circuit would still be intact.
Thanks for the advice. It's certainly made me think about the potential risks of the device failing. I'm leaning more towards the manual option now, though it would be a bit more hassle every time I want to use the car.
Wiring things into the fuse box and following wiring diagrams is beyond my capabilities I'm afraid!
Have a competent Jaguar specialist determine which circuit is causing the drain and replace the faulty component.
Each time the electrical system is disconnected from battery voltage all the emissions monitors are disabled and must be reset through several drive cycles. This may become an issue during MoT inspections.
The Jaguar 'transit-relay' or battery isolation devise disables the entire car EXCEPT the door modules.
The windows still need to 'drop' slightly when the doors are opened.
When I disconnect the XK batteries, I open both doors, open the boot lid and then disconnect.
Close the boot lid and doors, then you will not damage the door or glass.(the glass will not raise back up)
You can also locate and install an old Jaguar XK transit relay if you only drive the car very infrequently.(like a Jaguar sitting at the shipping port or dealer)
The windows and things like radio head unit will need resetting each time you 'wake the car'.
I use the generic battery disconnect devises on some of my cars.
The daily drivers don't need one but the 'once-in-a-while' cars do.
I got used to seeing them in the boot panel of Rolls Royce Silver Shadows years ago. They do keep batteries from slowly dying.
This an actual pic of an X100 transit relay or battery isolation devise.(one I forgot to return to the parts dept. OOOOPS)
Last edited by motorcarman; Nov 28, 2024 at 06:05 PM.
I think you are approaching the issue wrongheadedly.
Using a battery disconnect won’t do anything to keep the battery “tended” properly. Disconnecting the battery won’t keep it from losing voltage over time.
Our cars that have zero voltage drain still have batteries that need to be on a tender in order to keep all the 20+ year old degrading electronics happy. The alternator alone is not enough. It just isn’t.
If you can’t bring a battery tender to the car for whatever reason, then you need to take the battery out of the car and take it to someplace (your home ?) where there is a place that you can plug in a battery tender and keep the battery tended properly. Just isolating the battery from your voltage drain may sound like an effective bandaid, but it’s still not going to keep your car from having electrical issues in my opinion.
Primaryly because the battery voltage will continue to drop even when disconnected from the rest of your car’s electrical system.
That’s what all batteries do. Whether they are brand new or 5 years old. No battery can keep the voltage from dropping a little every day. It adds up.
they lose voltage when they are not being charged. Most newer cars can tolerate a battery that’s not quite 100%.
Not our cars.
These old cars, with their complicated and delicate electronics, cannot tolerate a battery that’s not 101%.
This forum is rife with posts from owners that have had numerous electrical gremlins that all disappeared when they started using a battery tender.
I think you are approaching the issue wrongheadedly.
Using a battery disconnect won’t do anything to keep the battery “tended” properly. Disconnecting the battery won’t keep it from losing voltage over time.
Our cars that have zero voltage drain still have batteries that need to be on a tender in order to keep all the 20+ year old degrading electronics happy. The alternator alone is not enough. It just isn’t.
If you can’t bring a battery tender to the car for whatever reason, then you need to take the battery out of the car and take it to someplace (your home ?) where there is a place that you can plug in a battery tender and keep the battery tended properly. Just isolating the battery from your voltage drain may sound like an effective bandaid, but it’s still not going to keep your car from having electrical issues in my opinion.
Primaryly because the battery voltage will continue to drop even when disconnected from the rest of your car’s electrical system.
That’s what all batteries do. Whether they are brand new or 5 years old. No battery can keep the voltage from dropping a little every day. It adds up.
they lose voltage when they are not being charged. Most newer cars can tolerate a battery that’s not quite 100%.
Not our cars.
These old cars, with their complicated and delicate electronics, cannot tolerate a battery that’s not 101%.
This forum is rife with posts from owners that have had numerous electrical gremlins that all disappeared when they started using a battery tender.
Battery Isolator Advice
