• Hi Guest why not show off your SEAT! (now fixed)
    You can now share your favourite car photos in the new media gallery including embedding pictures from your Instagram account.
  • Hi Guest! New high quality keyrings are now available to pre-order: order yours now.

How to make your 12v accessory socket permanently live

dw911

Active Member
Mar 30, 2013
1,038
4
My guess (and it's only a guess) is that by plugging the accessory socket fuse in at the "alternate" position you are bypassing the clever control features as well.

By the way, the charger that I leave plugged into my Passat if I'm working overseas during the winter months is ASIN: B004ZWV1JI on Amazon UK (sorry, I'm not allowed to post links yet, use the ASIN code in an Amazon search), it's clever enough to wind itself down to a trickle rather than make the battery "gas" like an old charger would. And it plugs into the accessory socket using the adapter ASIN: B0016LA5O8. There are no warnings about the possibility of damage when charging through the accessory socket, so I guess I'll just try it !

Postscript: having thought about it some more !

Even if the accessory socket is controlled by electronics, the actual switch will be either relay contacts or a P-channel MOSFET.

If it's a relay it won't mind passing current in the reverse direction. If it's a Power MOSFET there will be a reverse-protection schottky diode built into it, which will pass the reverse current. These protection diodes are typically rated higher than the FET itself, though there will be a greater volt drop which means there will be more power dissipation. But the charger won't try to push 20A, it's rated at 5A and in fact under the type of regular use to which I will put it, it'll deliver 5A only for a few seconds, if at all.

So I have stopped worrying about plugging-in the charger at the accessory socket as a winter precaution.

But if I ever find myself with a really flat battery, then I'll lift the bonnet and connect the charger in a more conventional way !
Another good smart charger is available ( periodically) from Lidl of all places, they are made by ctek, really good, paid about a tenner, it's the same charger inside that an Audi or Porsche stealer will fleece you 70+ quid for, just without the fancy badge.
I bought a few over the years for little used cars and bikes, they really are plug in and forget.
I've charged many cars via the accessory socket without issue and as you rightly said their is nothing in handbook to advise against it. In fact most main dealers will sell you a charger/battery maintaner that does just that and charges/maintains the battery via the accessory socket

By moving the fuse to the alternative position all your doing is bypassing the ignition switch part off the circuit, it still runs through the cars battery monitoring system, it's not just a direct live from the battery to the accessory socket
 
Last edited:

dw911

Active Member
Mar 30, 2013
1,038
4
It does have a door lock, it's hidden by a plastic cover with a little hole in it (on the underside) for you to use your key to prise off.
My mistake, it does indeed, if just looked, it's not obvious I guess you pull the whole painted piece off to access the door lock ?

The reason I didn't think it had, was I asked the seat garage how do I get into the car if the key battery goes flat, he said you can't so don't let it go flat :confused:
 
Last edited:

thefunkygibbon

Mk3 Leon Cupra 280
Jan 9, 2012
424
0
My guess (and it's only a guess) is that by plugging the accessory socket fuse in at the "alternate" position you are bypassing the clever control features as well.

By the way, the charger that I leave plugged into my Passat if I'm working overseas during the winter months is ASIN: B004ZWV1JI on Amazon UK (sorry, I'm not allowed to post links yet, use the ASIN code in an Amazon search), it's clever enough to wind itself down to a trickle rather than make the battery "gas" like an old charger would. And it plugs into the accessory socket using the adapter ASIN: B0016LA5O8. There are no warnings about the possibility of damage when charging through the accessory socket, so I guess I'll just try it !
I'm a little confused. you use a car battery charger plugged into itself to charge itself? That doesn't sound very logical to me.
Are you not supposed to plug it into another cars cigarette lighter socket?




Nice one on this post. This should be in the rather wrongly used "FAQ" subforum really. Although this site doesn't really seem to have any instructions as to what should be posted in there and as such its much the same as whats in this forum.
 
Last edited:

Branta

Active Member
Feb 22, 2015
36
0
Nottinghamshire
It's a regular 240V mains-powered charger for a car battery (but an "intelligent" one that drops back to a very low charge rate when the battery is charged, so it can be left connected indefinitely). Instead of lifting the bonnet and attaching to the battery with old-fashioned crocodile clips, it can be plugged into the cigar lighter socket (provided that does not get disconnected when leaving the car) to keep the battery topped-up.

I have my new Leon now, but I didn't even find the fusebox yet (of course it isn't where the handbook says it should be), let alone try my charger in the cigar lighter socket.

If I had devised a way of charging a car battery without plugging to anything other than the car itself then I think I could be driving a Bentley, not a SEAT :D
 

Seastormer

Cupra 280/CBF1000
Apr 25, 2014
4,026
274
64
Edinburgh (Scotland)
I use an Optimate 6, which connects to a lead left perm attached to the battery, it does the bike too as it automatically gives the battery the same charge it would get if taken for a drive/ride. It can't over charge and can be left attached to vehicles for months, and tells you if the battery has any faults too.
 

Stevan

Active Member
Apr 8, 2017
96
6
Musselburgh
I have a couple of things plugged into the 12 volt socket in front off the armrest
Now I've found it a bit of an inconvenience that it's only live with the ignition on
So I thought I'd see if I could make it permanently live and not controlled by the ignition, but I didn't really want to chop the wiring about

This is how I did in case anyone else wants to do the same

You need to pull down the glovebox (it's explained in the manual) to reveal the fuse box, in the middle of the fuse box you will see a yellow 20 amp blade fuse (location f40)
You will notice it sits a slight bit lower than the green 30 amp fuse to its left.
Remove the yellow 20 amp fuse,now move it up slightly until it is parallel with the green fuse next to it, push the fuse back in.

Your 12 volt accessories socket is now permanently live

Best of all its easily reversed if you change your mind

Now I was concerned that I may accidentally leave something plugged in and flatten the battery
But that can't happen as the battery monitoring system on the car will still shut it off if the battery starts to get low to leave enough power in the battery to still start the car

Anyway it may be of use to some of you

Cheers

This is perfect - thankyou very much, the hardest bit is getting the glove box down (Right Hand Drive version).
Both my old Mk1 Leons had permanent 12v sockets - it's essential for me to charge my efag batteries overnight when camping at music festivals.
 
Last edited:

daniel575

Active Member
Apr 2, 2014
123
1
How exactly do I get to those fuses in the glove box? Can someone perhaps post a picture showing how to open the glove box to get to the fuses? I don't see it explained very well in the manual (page 250). To make it even funnier, I never even realised the small glove box existed at all, never used it in 4 years and 225,000 km. Only discovered it now. But I don't see how to get to the fuses that must be behind it somewhere.
 

chrisRibiza

Active Member
Sep 27, 2007
1,172
44
Newtownards, Northern Ireland
Basically you just need to drop the door.

Open the glove box
Empty it
Get a long flat head screwdriver and push it in the gap beside the door, there's a piece of plastic on either side which will push then you just need to pull the door towards you.

The door will drop and give you access to the fuses and the pollen filter housing.
 

daniel575

Active Member
Apr 2, 2014
123
1
Basically you just need to drop the door.
(....)
We're talking the small glovebox (sunglassbox or whatever) on the *right* side of the car, or the big one on the *left*? (UK car.)

I got into the area behind the small glovebox on the right but it's pretty much empty, definitely no fuses in there.
 

kazand

Is powered by Medtronics
Jun 6, 2010
4,154
67
Brum
We're talking the small glovebox (sunglassbox or whatever) on the *right* side of the car, or the big one on the *left*? (UK car.)

I got into the area behind the small glovebox on the right but it's pretty much empty, definitely no fuses in there.
Big one on the left.
 

daniel575

Active Member
Apr 2, 2014
123
1
Yay, done. No screwdriver, I just pushed it in from both sides and managed to get it down. Tested and it works fine. Thanks!!
 

zeffania

Active Member
Nov 4, 2016
393
112
Nice one OP

Making a nice list of mods I need to do when I can finally get an FR in a year :cry:

Taking one for a test drive last weekend had to be done, but will be a killer waiting so long
 

SeatLog

Active Member
Dec 1, 2018
1
0
This is perfect - thank you, the hardest bit is getting the glove box down, squeeze technique (Right Hand Drive version) Also needed the hint for the fuse box location as not in the handbook...
 
Dec 18, 2019
25
0
Sorry for the really old bump, thought better than a new thread as my old Ibiza was perminantly live and my new Leon not! I can't get it right haha. This is a Pic of my fuse box below if I remove one of the yellow fuses my 12v stops working so do I touch that one or is it another? Also I have a 2007 mk2

Sorry for ignorance haha
 

Attachments

Lozzy15

Mods mods mods
Staff member
Moderator
Mar 24, 2015
384
201
Ilkeston, Derbyshire
Sorry for the really old bump, thought better than a new thread as my old Ibiza was perminantly live and my new Leon not! I can't get it right haha. This is a Pic of my fuse box below if I remove one of the yellow fuses my 12v stops working so do I touch that one or is it another? Also I have a 2007 mk2

Sorry for ignorance haha
This thread was in response to the MK3 Leon, the MK2 is most likely wired differently from what has been discussed in this thread so I don't know if it's as easy for you to make yours perm live as described here. Might be worth making a thread in the MK2 forums and asking there, someone with more knowledge of the MK2 platform than me may be able to help (y)
 
SEATCUPRA.NET Forum merchandise