# How to connect something to a car battery when there is only one terminal?

#### CaptainBrazuca

Joined May 5, 2024
3
Sorry I don’t know where to ask this or how to find this information on google.
My understanding to electricity is close to none.
I recently got a dash cam and wanted to hardwire it to the fuse box. So in the hardwire kit came 3 terminals, one for battery (always on), one for ignition (when the car is running) and a ground. I have attached a photo of it for reference.
So my question, how does it close circuit if there is only one terminal going to the fuse box (even though I understand the ground is connected to any part of bare metal in the car.
The reason I want to understand this is because there is another fuse box where I can tap into it to have a constant power for some lighting inside the van. But it uses the same concept, I can only plug one terminal, but where should I plug the other terminal from the led? Does grounding to the car will work, or do I have to close circuit back to the battery?

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#### Ya’akov

Joined Jan 27, 2019
9,264
Welcome to AAC.

Your car‘s battery has the negative terminal bonded to the car’s chassis. Anything that is part of that chassis (electrically) is the functional equivalent of the negative terminal.

So, yes—the positive (+12V) will be from the fuse box or the battery terminal, or something else that is connected back to the battery’s positive terminal while the negative (0V) connection is made to the metallic chassis, the battery terminal, or anything that is connected back to the terminal.

Joined Jul 18, 2013
28,825
It would be preferable to connect the 12+ve to the 'Ignition-on' fuse buss, if no spare fuse available then use an inline fuse holder.

#### CaptainBrazuca

Joined May 5, 2024
3
Welcome to AAC.

Your car‘s battery has the negative terminal bonded to the car’s chassis. Anything that is part of that chassis (electrically) is the functional equivalent of the negative terminal.

So, yes—the positive (+12V) will be from the fuse box or the battery terminal, or something else that is connected back to the battery’s positive terminal while the negative (0V) connection is made to the metallic chassis, the battery terminal, or anything that is connected back to the terminal.
This! Thank you so much now I understand why it makes connection back to the battery. It’s amazing how this things works. Thanks

#### CaptainBrazuca

Joined May 5, 2024
3
It would be preferable to connect the 12+ve to the 'Ignition-on' fuse buss, if no spare fuse available then use an inline fuse holder.
Thank you for taking the time to reply. The dashcam I already got it running through the step by step instructions and some YouTube videos on how to find the right fuse with a multimeter. But in the process I found another fuse box that actually have some switches mounted to the dash where I can use to turn the lights on and off, so now I’m going to try that. But I just didn’t understand how it worked as It only has one terminal.

Joined Jul 18, 2013
28,825
Looks like the BLK (-ve) is the spade terminal for chassis connection!?

#### Tonyr1084

Joined Sep 24, 2015
7,991
I've hooked up Two Wire systems where one wire, the black wire, gets screwed under a bonded metal contact point. Don't let that scare you - a bonded metal contact point is just a bare metallic surface. No paint, no plastic, nothing to impede the electrical contact. The other wire (in my case) was plugged into the fuse box where a switched power source was available. Whenever the car was on or in ACC mode the camera had power.

I'm not familiar with the yellow wire on your kit. It might be intended to have a constant power source (not switched) to retain memory and possibly to power the G-Sensor function, where if someone hits your car the camera automatically turns on for a set period of time and record something. Possibly the person who hit your car. But that is pure guesswork on my part.