Technical 12 volt accessory supply, always live

[Fillipe]

Apologies if this isn't in the right section, but as it relates to the 2012+ Panda, it seemed logical.

I want to put a 12v power supply in the boot that I can use without needing the ignition on (10A,120w max). Ideally I would run it straight from the battery, but I can't see an easy way to route any cable into the cab area from the bonnet. Has anyone done this, and if so how did you route the cable, or is there a point in the car where I can pick up an always live 12v supply?

Hope someone can help point me in the right direction!

 

[murphyv310]

You'd normally be able to pick up a decent live supply from the unswitched side of the ignition switch. There could also be a constant live in the internal fuse box.
Big snag is the lack of a decent workshop manual for reference.

Don't forget to add an inline fuse, a 15amp to give a little headroom for your use and remember the standard batteries are not the best capacity by a long way.

 

[Fillipe]

Thanks Trevor,
I already have the wiring and an inline fuse 'lined up' . I shall stick to 10 amps, as I won't be using it for high load stuff, but I'm wary about where to 'tap' from. As you say, the lack of a workshop manual makes this sort of thing more nerve wracking. I'm confident enough to do a good fitment, but not enough to identify the best place to pick up the feed from, hence the question

 

[murphyv310]

Following normal practice there would be a minimum of three leads from the back of the ignition switch. One is the feed from the battery perhaps via a mega fuse, one that goes to the ecu and other ignition controlled circuits and one for starter operation.
These days a lot more circuits are controlled so there could be other wires.
With a multimeter you should be able to find the live feed and if the cable is thick (3-4mm) then it will be fine for your use.
Running the lead from the battery is the safest and best but always beware of chafing if you can't see the entry and exit points well plus of course any double skinning that could cause problems.

 

[jrkitching]

Running the lead from the battery is the safest and best but always beware of chafing if you can't see the entry and exit points well plus of course any double skinning that could cause problems.

Also if you have a S/S car, don't connect anything directly to the negative battery terminal - the second negative terminal the other side of the IBS should be used instead, or S/S may not work properly.

In days past, most circuits used the car chassis for the return feed, but the tendency now is for these to be hardwired.

 

[murphyv310]

Also if you have a S/S car, don't connect anything directly to the negative battery terminal - the second negative terminal the other side of the IBS should be used instead, or S/S may not work properly.

In days past, most circuits used the car chassis for the return feed, but the tendency now is for these to be hardwired.

Are you saying then the chassis is now floating with a negative busbar used for all negative returns?
Certainly this doesn't apply to the Panda as the battery negative is grounded to chassis in the normal way. No stop start on the 1.2.

 

[Fillipe]

So a furtle around with a multimeter revealed that the supply to the fuseboard behind the glove box is always live,

and not switched via the ignition. I tapped into this lead, and soldered a fused lead to my accessory socket, which I have mounted in a project box on the left rear quarter.

The cable is run under the plastic trim along the nearside door bottoms, and up through the trim beneath the rear seat (photo is before I finished tucking it away!). Jobs a good 'un

 

[murphyv310]

Good result indeed.
Thanks for taking the time to check out the fuse box and your finished job.
Always good to get info especially when there is very little info on a car these days.
Now all we need is a workshop manual.