Switched 12 volt connection

jelloslug · Nov 18, 2014

There have been a few people (myself included) that have been looking for an easy to access 12V connection that turns off with the car. I found one right on the fuse box:

I do not know which fuse these circuits are on so I suggest that you install an inline fuse to your device if you decide to use these connections.

Bunter · Nov 18, 2014

jelloslug said:
There have been a few people (myself included) that have been looking for an easy to access 12V connection that turns off with the car. I found one right on the fuse box:

I do not know which fuse these circuits are on so I suggest that you install an inline fuse to your device if you decide to use these connections.

The outlets under the dash and in the boot are switched 12V outlets I think.

Bill

jelloslug · Nov 18, 2014

Bunter said:
jelloslug said:

There have been a few people (myself included) that have been looking for an easy to access 12V connection that turns off with the car. I found one right on the fuse box:

I do not know which fuse these circuits are on so I suggest that you install an inline fuse to your device if you decide to use these connections.

Click to expand...

The outlets under the dash and in the boot are switched 12V outlets I think.

Bill

Nope, they stay on for at least 20 minutes.

Marki3 · Nov 21, 2014

Hi,

What kind of terminals are those? Any idea what kind of amperage we could draw off them? I would love to use the switched terminal to power a 200W sub woofer. So, would need somewhere around 16 amps.

Thanks for posting that info. Very useful.

Mark.

jelloslug · Nov 23, 2014

Marki3 said:
Hi,

What kind of terminals are those? Any idea what kind of amperage we could draw off them? I would love to use the switched terminal to power a 200W sub woofer. So, would need somewhere around 16 amps.

Thanks for posting that info. Very useful.

Mark.

If you don't think that it has the current rating that you need you could always use it to power a relay.

jadnashuanh · Nov 23, 2014

Keep in mind that the 12vdc battery isn't very large, and every watt going into keeping it charged so the computers will continue to run and your lights, fans, etc. will work takes away from your max range. I have no idea how big the DC-DC converter power supply in the i3 is, but there's a limit on how much power it can supply to the 12vdc battery. Obviously, if you were constantly using 200W you'd soon be deaf and it wouldn't matter, but anything you add to the vehicle has an effect on your range both because of the weight and the power usage. It's one thing when you have an ICE and an alternator, it's entirely a different concern when you only have your main battery pack to sustain you.

Marki3 · Nov 23, 2014

Thanks for the input. 200 watt peaks are rare. Having run a similar sub in different setting I found average pull of only 20-30 watt. It has level adjustment and about half volume would be plenty. So, I suspect that adding the sub would have minimal measurable effect. I plan to have it switchable and if I did see a detrimental effect on range could easily switch it off if necessary.

jadnashuanh said:
Keep in mind that the 12vdc battery isn't very large, and every watt going into keeping it charged so the computers will continue to run and your lights, fans, etc. will work takes away from your max range. I have no idea how big the DC-DC converter power supply in the i3 is, but there's a limit on how much power it can supply to the 12vdc battery. Obviously, if you were constantly using 200W you'd soon be deaf and it wouldn't matter, but anything you add to the vehicle has an effect on your range both because of the weight and the power usage. It's one thing when you have an ICE and an alternator, it's entirely a different concern when you only have your main battery pack to sustain you.

ultraturtle · Nov 26, 2014

Marki3 said:
I would love to use the switched terminal to power a 200W sub woofer. So, would need somewhere around 16 amps,

I have a slightly more elaborate sound system upgrade in our Plug-In Prius, which has a tiny 12 volt battery, just like the i3:

http://priuschat.com/threads/total-...essor-amp-and-subwoofer.112102/#axzz3KBDPF3cn

The 12 volt system is more than adequate to power the 500 watt subwoofer amp and 4 X 100 watt sound channels. I power the system directly from the battery, with its own inline fuse. Power sensing comes from the car's original sound system output to the JBL MS-8, which completely powers down the system when the car is turned off.

Folks tend to not make a distinction between power potential, and power actually used. While the system is capable of outputting as much as 900 watts, I've taken measurements at a sound pressure level louder than I would ever consider listening and found a peak of about 70 watts, and an average less than 20 watts - no strain whatsoever on the 12 volt system.

By the way, that works out to a potential impact on range of no more than 1/10th of 1 percent, or about 143 yards per hour of the i3's 81 mile range, and then only at a continuous, painfully loud listening volume. At normal volume levels, probably closer to 15 yards per hour or so.

Bunter · Nov 26, 2014

ultraturtle said:
I have a slightly more elaborate sound system upgrade in our Plug-In Prius, which has a tiny 12 volt battery, just like the i3:

http://priuschat.com/threads/total-...essor-amp-and-subwoofer.112102/#axzz3KBDPF3cn

The 12 volt system is more than adequate to power the 500 watt subwoofer amp and 4 X 100 watt sound channels. I power the system directly from the battery, with its own inline fuse. Power sensing comes from the car's original sound system output to the JBL MS-8, which completely powers down the system when the car is turned off.

Folks tend to not make a distinction between power potential, and power actually used. While the system is capable of outputting as much as 900 watts, I've taken measurements at a sound pressure level louder than I would ever consider listening and found a peak of about 70 watts, and an average less than 20 watts - no strain whatsoever on the 12 volt system.

By the way, that works out to a potential impact on range of no more than 1/10th of 1 percent, or about 143 yards per hour of the i3's 81 mile range, and then only at a continuous, painfully loud listening volume. At normal volume levels, probably closer to 15 yards per hour or so.

With that in mind I'm even more curious than I was why the switched outlets already in the i3 are not sufficient even if they stay live for a short period after turning the car off?

Bill

ultraturtle · Nov 26, 2014

Bunter said:
With that in mind I'm even more curious than I was why the switched outlets already in the i3 are not sufficient even if they stay live for a short period after turning the car off?

Bill

They're plenty sufficient for insignificant loads like audio entertainment. I wouldn't try to run a microwave, however...

DarrenG · Jul 9, 2015

I know this is an old thread but currently trying to wire in a BlackVue drive recorder and struggling to identify a suitable ignition controlled feed in the fusebox. Can anyone help identify a suitable 5A fused feed I can patch into?

Jeffj · Jul 10, 2015

There are a lot of posts (with pictures) in the Facebook group about putting in dashcams. Mary Demarest-Parran posts a lot there and has good info. She is also a moderator on The Circuit - the official BMW forum, so if you are anti-Facebook, you can post there and probably get an incredibly detailed response within an hour. She's extremely helpful with i3 matters.

DarrenG · Jul 10, 2015

Thank you, I'm a member of the i3 group so will ask there.

jelloslug · Jul 10, 2015

Did you look at the first pic in this thread?

DarrenG · Jul 10, 2015

Yes but the locations indicated are of an unknown type. Much simpler if I can simply tap into an existing fused location.

crossie · Jul 26, 2015

jadnashuanh said:
Keep in mind that the 12vdc battery isn't very large, and every watt going into keeping it charged so the computers will continue to run and your lights, fans, etc. will work takes away from your max range. I have no idea how big the DC-DC converter power supply in the i3 is, but there's a limit on how much power it can supply to the 12vdc battery.

It's 150W.

jadnashuanh · Jul 26, 2015

Humm, 12.5A at 12vdc isn't a lot to keep the lights on, the fans blowing, the computers and screen lit and running, and the accessories powered up! Quite a bit different than my ICE which has a 200A alternator and a huge storage battery...I'd be careful about what I had plugged into my i3.

DarrenG · Jul 27, 2015

FWIW I used unused fuse location #51 in the end, it's ignition switched. Camera now installed and working AOK.

crossie · Jul 29, 2015

DarrenG said:
FWIW I used unused fuse location #51 in the end, it's ignition switched. Camera now installed and working AOK.

Where on the windscreen did you install the camera? I'm having trouble finding a stop that's out of the way and not blocked by the ACC camera.

DarrenG · Jul 30, 2015

I don't have ACC on mine but installed it directly below the sensor shroud with the cable running inside it to keep it tidy. It's not visible from the driving seat.

Switched 12 volt connection

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