Battery Cables and Terminals: Is Red Positive Or Negative?
When connecting batteries, jump starters, jumper cables, and similar to the car's or similar batteries, it is very important to know which cable and terminal post are positive and which ones are negative.
Also, it is very important to know which one to connect or disconnect first.
Not knowing such information can be dangerous since car batteries and jump starters are able to provide huge currents, even when not fully charged.
Updated: November 6, 2023.
Red or Black, Positive or Negative: Quick Answer
To keep things as simple as possible, remember that the red is positive and that the black is negative:
- battery terminals: positive terminal post is the red one (plus sign), negative battery terminal post is black one (minus sign),
- jumper cables: positive cable (positive wire), commonly with the alligator clamps, is the red one and is connected to the positive (red) battery terminal, and the negative cable (negative wire) is the black one and is connected to the negative (black) battery terminal,
- jump starters: positive cable (positive wire), again, commonly with the alligator clamps, is the red one and is connected to the battery's positive (red) terminal, and the negative cable (negative wire) is connected to the battery's negative terminal (black).
Knowing this is very important - when connecting the battery to the battery or jump starter to the battery, if they are short-circuited, huge currents (thousands of Amps) will melt the insulation within seconds and most probably start a fire - that is how these cables can get hot if something is connected in the wrong way.
Car Battery and Jump Starter Cables Connecting Order
When connecting the battery to the battery or jump starter to the battery, remember that the car is common ground (in most cases) - it has a chassis connected to the negative battery terminal post (also known as "minus") via black cable.
Thus, when connecting the battery to the battery or jump starter to the battery, always connect the positive (red) cable first and only then the negative (black) cable.
When disconnecting the battery from the battery or jump starter from the battery, always disconnect the negative (black) cable first and only then remove the positive (red) cable.
This way, if the cable clamps are accidentally dropped on the exposed metal of the chassis, there will be no short circuit.
Note: when using jumper cables or jump starter, if You are unsure about the exact procedure, it is good practice to check the instructions/manual - better safe than sorry...
DC Electronics Cable Colors: Red vs. Black
In the realm of DC electronics, professionals often work with DC power supplies in various applications such as LED systems, solar power, battery operations, DIY projects, and microcontroller-based endeavors.
In this context, two fundamental polarities are recognized: positive and negative.
The positive voltage typically exceeds 0V, with standard levels being 3.3V, 5V, and 12V, among others. Conversely, the negative potential generally aligns with 0V and is commonly referred to as ground.
A universally accepted convention in DC electronics dictates that the color red signifies a positive polarity, while black denotes a negative one.
This is evident in the wiring of, for example, USB cables, both the traditional USB-A and the contemporary USB-C types. In these cables, the red wire transmits the VCC or positive voltage, whereas the black wire connects to the ground, representing 0V.
However, for many other DC systems, wire color codes are more complex than this - some systems are, for example, earthed, and some are not, which dictates the use of wires with different colors.
For the complete wire color codes (AC/DC), feel free to check our Quick Guide to Electrical Wire Color Codes article.
Car Battery and Jump Starter Cables Starter Frequently Asked Questions
Here are some of the most common Frequently Asked Questions about battery and jump starter cables.
Does red go on positive?
Yes, the red cable goes/is connected to the positive terminal of the battery, which is labeled with "+" and is also red.
Is red usually negative?
No, red cable or red battery terminal is never negative.
Do I connect black or red first?
When connecting the car battery to the car battery (good battery and bad battery) or the jump starter to the car battery, the red cable ALWAYS goes first.
When disconnecting, the order is another way around - disconnect the black cable first.
Why is the positive terminal red?
A negative battery terminal is connected to the car's chassis, which is common ground - touch it, and nothing will happen because you are also grounded via your feet.
On the other hand, the color red is a synonym for danger. While 12V DC is not dangerous to humans, it is used to label cables and wires with a higher voltage than the common ground.
Is red positive or negative?
The red cable/red wire or red battery terminal is positive.
Is negative red or black?
The black cable/wire or black battery terminal is negative.
Battery terminals are all black and dirty; how do you check which one is positive and which one is negative?
If the battery terminals are of the same color for various reasons (age, dirt, damage, etc.) and you can't figure out which one is positive and which one is negative, the best course of action is to use a multimeter, preferably a digital one. Set it to DC voltage, at least 15-16V range (or use an auto-ranging multimeter), and check the battery terminals.
Note: A decent multimeter will do just fine.
Few Final Words
Battery jumper cables or battery jump starters can be of great help in certain situations. When used properly, they are a very safe alternative to the car's dead battery.
However, when not used properly, they can cause fire, damage, injuries, or worse. Always, if unsure, check the Owner's Guide or seek professional help.
Also, when connecting cables, it is highly recommended to wear protective gloves and goggles.
