Hi all-

I have a 2009 flying spur and i need to run a 100w siren/speaker unit that requires power directly from the battery, but i'm not running lines from the batteries in the trunk to the front (behind gauge cluster, or under the hood). I've located a million places to find ground power, but i can't find a place to tap for max (+) that goes directly to the battery, on 24/7 wheher car is on or off (I'm looking for thickest gauge wire, no fuses in line, etc).

All the places i've looked for (+) thus far has lead to melted wires and blown fuses. And getting "behind" (not to the front of) the knee area fuse box is a B!*CH!.

Any suggestions? I can take the power from anywhere behind the gauge cluster (not glove box) or anywhere under the hood. I need this (+) directly from the battery, on all the time, and in no-way connected to any other fuses or systems. I already (somehow) blew out the satelite radio by trying to tap into the #9 fuse for "tv tuner"

Thanks for ANY input!! Also does it matter where i grab ground power (and i guess + also) knowing that these cars have TWO batteries in the trunk?

 

Right side of engine bay (U.S.passenger side) at the firewall remove the right side air box. Look down a bit is the main power lead from the battery to the engine bay. That's as direct as It gets. The terminal junction has a13 mm nut remove it and connect. Good luck.
PS. Don't catch anything on fire😉

 

thanks for the quick response! I took a look and i'm not finding anything there but two bolts about 2" apart, but im not sure if this is what you're referring to?

And are there any pictures of what you're referring to?

Does it matter where i grab ground power considering there are two batteries?

 

Ground off the body or engine. Connect grounding cable to a sturdy bolt in the engine compartment. Would be easier if you sent me a picture of what you think is the positive terminal.

The description sounds like you found it. You could also take a voltage tester and apply it to that terminal and a body ground and see if you get 12 volts.

 

Here’s what I see. Can you edit the picture to circle what I need?

 

 

Are both of those bolts (+) from the same battery? Or is one for one battery and one for another? When i play around with these bolts with my voltmeter, sometimes i get indications that they're not from the same source, and once that one was grounded.

And does it matter where i tap (-) if i use one of these bolts for (+)?

 

Don't know if it makes a difference which one you tap for 12 volts. Perhaps disconnect the starter battery which is the rear right battery that won't require reprogramming your radio and seats Etc. Then you can determine which side is which. Indeed one is for the starter and the other side is for the general accessories.

Read this before disconnecting batteries.

A sturdy ground on the engine block or body is fine. There's nothing special about grounding, other than common sense. Usually a strong bracket with a bolt holding it in place is a good spot to unbolt and tap in.

 

 

You have two leads that go from each battery. The Bentley has a dedicated battery just for the starter the other battery is for the accessories. That Junction that you're looking at is the division between the two sides. Suggestion of disconnecting the starter battery will show which side that goes to, it will not have 12 volts.

You're overthinking the whole process 12 volts is 12 volts. This car is not like a Chevrolet with one battery or a diesel truck with two that power everything. Bentley partitions the batteries for different functions.

 

OK guys i found the answer! I took your suggestion of disconnecting the starter battery and testing for voltage on each lead in the engine area. I found out that the RIGHT bolt (if looking directly at the two under the hood) is the accessory battery, while the LEFT bolt is ONLY to the starter battery. So I had to tap off of the RIGHT bolt. If I tapped from the LEFT bolt, I'd risk draining the starter battery.

When i disconnected the accessory battery (the left side battery in the trunk), there was NO power to the RIGHT bolt. That's how i determined it.

 

Perfect