Are lighter sockets always on?

Kobajagi · 08-20-2019, 04:34 PM

Hello everybody, after searching far and wide I've got a mix of answers.

I own a 2013 335xi Msport (Canadian version with only a single 12v socket by the cupholders

)

I purchased a 12v socket from BMW and am going to install it under the passenger-side glovebox and run it to the fuse box in the trunk.

I'm planning on using the large (ATC) "add-a-circuit" tap to fuse #162 which is one of three fuses for 12v sockets (162 is for the trunk socket).

there are a few DIY out there that use the mini add-a-circuit, and use the HomeLink fuse #146, but that is only a 5amp fuse and I would like to be able to use up to 20amp to run a dashcam/charge a phone simultaneously.

is this fuse an always-on type?
or does it power off after some time?
or does it depend on the ignition?

Thanks!

chowser51 · 08-20-2019, 05:03 PM

I know homelink turns off after opening the door. I have to remember to hit the button to close the garage door before exiting

Billfitz · 08-20-2019, 05:25 PM

My console outlet goes on when I start the car, goes off a few minutes after I lock it. If I don't lock the car after exiting it stays on for quite some time but eventually shuts off.

Kobajagi · 08-20-2019, 06:10 PM

So I decided to use a multimeter and sit inside the car while it was locked to see whether it was always-on or not, and I got some interesting results.

Fuse # 162 stayed on at 12.8V for the first 3 minutes. After that, it slowly began to lower its voltage for ~5 minutes until it hit 2V and then it REALLY slowed down. For the next 5 minutes it made it to 1.2V (but by that time I was getting hot so I decided to unlock the car and I watched the voltage jump back up to 12.8V.

So I'm going to safely assume that it turns completely off after about 15 min and so I will be using the fuse for my accessories.

Does anyone know why it trickles down to 0v rather than immediately cutting the power?

Billfitz · 08-20-2019, 08:54 PM

Anything plugged into it while it wound down? My auxiliary LED DRLs run off that fuse, and they don't gradually fade, they shut off abruptly.

Kobajagi · 08-20-2019, 09:35 PM

Quote:

Originally Posted by Billfitz

Anything plugged into it while it wound down? My auxiliary LED DRLs run off that fuse, and they don't gradually fade, they shut off abruptly.

no, only the multimeter was touching it, the fuse wasn't even in it

Billfitz · 08-21-2019, 07:48 AM

My educated guess is that some sort of capacitive storage on that circuit caused the voltage to gradually decrease in absence of a load.

08-20-2019, 04:34 PM	#1
Kobajagi New Member 0 Rep 6 Posts Drives: 2013 335xi Msport Join Date: Aug 2019 Location: Toronto iTrader: (0)	Are lighter sockets always on? Hello everybody, after searching far and wide I've got a mix of answers. I own a 2013 335xi Msport (Canadian version with only a single 12v socket by the cupholders ) I purchased a 12v socket from BMW and am going to install it under the passenger-side glovebox and run it to the fuse box in the trunk. I'm planning on using the large (ATC) "add-a-circuit" tap to fuse #162 which is one of three fuses for 12v sockets (162 is for the trunk socket). there are a few DIY out there that use the mini add-a-circuit, and use the HomeLink fuse #146, but that is only a 5amp fuse and I would like to be able to use up to 20amp to run a dashcam/charge a phone simultaneously. is this fuse an always-on type? or does it power off after some time? or does it depend on the ignition? Thanks!
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08-20-2019, 05:03 PM	#2
chowser51 Colonel 2025 Rep 2,808 Posts Drives: F33 430 and F39 M35i Join Date: Feb 2009 Location: Cleveland, OH iTrader: (3) Garage List 2018 BMW 430i xDrive [0.00]	I know homelink turns off after opening the door. I have to remember to hit the button to close the garage door before exiting
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08-20-2019, 05:25 PM	#3
Billfitz Lieutenant General 8243 Rep 16,081 Posts Drives: '15 328iX GT Join Date: Jan 2015 Location: New Hampshire iTrader: (0)	My console outlet goes on when I start the car, goes off a few minutes after I lock it. If I don't lock the car after exiting it stays on for quite some time but eventually shuts off.
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08-20-2019, 06:10 PM	#4
Kobajagi New Member 0 Rep 6 Posts Drives: 2013 335xi Msport Join Date: Aug 2019 Location: Toronto iTrader: (0)	So I decided to use a multimeter and sit inside the car while it was locked to see whether it was always-on or not, and I got some interesting results. Fuse # 162 stayed on at 12.8V for the first 3 minutes. After that, it slowly began to lower its voltage for ~5 minutes until it hit 2V and then it REALLY slowed down. For the next 5 minutes it made it to 1.2V (but by that time I was getting hot so I decided to unlock the car and I watched the voltage jump back up to 12.8V. So I'm going to safely assume that it turns completely off after about 15 min and so I will be using the fuse for my accessories. Does anyone know why it trickles down to 0v rather than immediately cutting the power?
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08-20-2019, 08:54 PM	#5
Billfitz Lieutenant General 8243 Rep 16,081 Posts Drives: '15 328iX GT Join Date: Jan 2015 Location: New Hampshire iTrader: (0)	Anything plugged into it while it wound down? My auxiliary LED DRLs run off that fuse, and they don't gradually fade, they shut off abruptly.
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08-21-2019, 07:48 AM	#7
Billfitz Lieutenant General 8243 Rep 16,081 Posts Drives: '15 328iX GT Join Date: Jan 2015 Location: New Hampshire iTrader: (0)	My educated guess is that some sort of capacitive storage on that circuit caused the voltage to gradually decrease in absence of a load.
	Appreciate 0 Quote