jelloslug
Posts: 226
Joined: Thu May 08, 2014 4:03 pm

Switched 12 volt connection

Tue Nov 18, 2014 2:23 pm

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:

Image

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
Posts: 372
Joined: Sun Nov 17, 2013 3:41 pm
Location: South Central England

Re: Switched 12 volt connection

Tue Nov 18, 2014 2:49 pm

jelloslug wrote: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:

Image

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
Born Electric 15.03.14

jelloslug
Posts: 226
Joined: Thu May 08, 2014 4:03 pm

Re: Switched 12 volt connection

Tue Nov 18, 2014 6:02 pm

Bunter wrote:
jelloslug wrote: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:

Image

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
Nope, they stay on for at least 20 minutes.

Marki3
Posts: 36
Joined: Thu Jul 31, 2014 8:11 am

Re: Switched 12 volt connection

Fri Nov 21, 2014 12:26 pm

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
Posts: 226
Joined: Thu May 08, 2014 4:03 pm

Re: Switched 12 volt connection

Sun Nov 23, 2014 3:48 pm

Marki3 wrote: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
Posts: 5034
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Switched 12 volt connection

Sun Nov 23, 2014 4:43 pm

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.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

Marki3
Posts: 36
Joined: Thu Jul 31, 2014 8:11 am

Re: Switched 12 volt connection

Sun Nov 23, 2014 9:10 pm

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 wrote: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
Posts: 439
Joined: Sun Dec 30, 2012 11:17 am
Location: Peachtree City, Georgia USA

Re: Switched 12 volt connection

Wed Nov 26, 2014 6:41 am

Marki3 wrote: 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:
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
Posts: 372
Joined: Sun Nov 17, 2013 3:41 pm
Location: South Central England

Re: Switched 12 volt connection

Wed Nov 26, 2014 1:35 pm

ultraturtle wrote: 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:
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
Born Electric 15.03.14

ultraturtle
Posts: 439
Joined: Sun Dec 30, 2012 11:17 am
Location: Peachtree City, Georgia USA

Re: Switched 12 volt connection

Wed Nov 26, 2014 2:15 pm

Bunter wrote: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...

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