Which Side Of Battery Is Positive? Here’s How To Tell

Connecting the wrong battery terminal to another battery terminal can result in a short circuit that can be damaging to the car, the batteries, and even your health, so it’s important to make sure you know which is which.

Unfortunately, car manufacturers don’t always put positive and negative signs on their battery terminals, so it can be hard to tell if you’re making an error if they’re unmarked. Fortunately, there are some easy ways to identify them as long as you know what you’re looking for and where to look.

How Can You Tell Which Terminal Is Which?

Most unmarked car battery terminals use a + or – to indicate polarity, although not every manufacturer uses these indicators. However, any manufacturer that does not use a symbol to indicate polarity is violating National Electrical Code regulations.

Because of this violation, it is possible that a positive and negative terminal is used for each cable; however, under normal circumstances, most car batteries use one positive and one negative terminal per cable. The key to identifying unmarked car battery terminals is learning how they look so you can easily tell which one is positive and which one is negative.

Car battery with polarity indications.

Once you know how they look, you will be able to easily identify them in future situations where you need to connect a new terminal or replace an old one. You should take note of several things when inspecting your battery terminals:

  • First, determine if there is a red or black wire connected to each terminal.
  • Next, inspect both ends of each wire for color markings indicating polarity.
  • Finally, look at both ends of each wire for physical markings indicating polarity.

If you find a red or black wire with no marking on either end, it is likely that both wires are attached to opposite terminals. If you find a red or black wire with no marking on either end but find that one end has a different texture than the other end, then it is likely that one of those wires goes to the ground and one goes to the power.

Expert Tip: In order to ensure your safety while working around your car battery, always wear protective clothing such as long sleeves and rubber gloves.

Unmarked Battery Cables

Unmarked car battery cables can be confusing for people. The cable could have a red, black, or white marking and it is hard to tell which one is positive and which one is negative without knowing something about cars. But with a few tips, you can make it easier to identify unmarked battery cables.

If you connect a black wire from your car battery to your body’s chassis, you will probably get electrocuted instantly. This is because all unmarked car battery cables are considered to be dangerous by definition.

For example, an unmarked black car battery cable may look like a ground (negative) terminal but in fact, it might be an ignition circuit wire that carries 12 volts of electricity. In case of an accident, these wires might cause severe burns on human skin if they come into contact with it.

So How Do You Test An Unmarked Car Battery?

You should always use a voltmeter when testing an unmarked car battery cable. It should help you identify whether there is any voltage coming out of it. Turn off all electrical appliances inside your vehicle before testing any electrical component including an unmarked car battery cable.

Make sure that no one touches anything metallic while testing as metal conducts electricity quite well even when it does not seem so.

What Happens When A Negative And Positive Terminal Are Connected Together?

Let us assume that we have two terminals marked + and – on both ends of a car battery cable. Now let us assume that we attach a third terminal marked + to one end of our first car battery cable.

Now, what happens when we attach another unmarked terminal marked – to another end of our first car battery cable? We know that connecting two opposite terminals together will result in zero current flow through them.

How To Test A Car Battery?

It is simple to test a car battery in order to determine whether or not it needs to be replaced. The following are some simple steps that should help you if you are ever wondering how to check if your car battery is dead or alive.

  • First, remove all jewelry from your hands and put them on a non-conductive surface such as wood or plastic. Also make sure that there is nothing metallic attached to your people such as a belt buckle, clothing fasteners, or an ID badge.
  • Next, take a 12-volt test light (also known as a voltage tester) and connect one end of it to either terminal of your car battery (in most cases, these will be marked with + and – signs).
  • Then touch the other end of your voltage tester to any unpainted metal surface under your hood. If everything has been done correctly, you should see some lights at work on your voltage tester.

Now that you know how to test a car battery, let’s move on to jumpstarting a car. Jumpstarting a vehicle can be accomplished by using jumper cables and another working vehicle. Make sure both vehicles are turned off before attempting to jumpstart either one. Connecting jumper cables incorrectly can result in severe injury or even death!

Let’s say that you are now confident about being able to test a car battery, but what happens when it won’t start? Well, the first thing is first – don’t panic! There could be several reasons why your car won’t start up. The most common reasons include low fuel levels, dirty spark plugs, corroded batteries, or faulty starter motors.

When your engine won’t turn over, chances are good that your car battery is defective or close to dying. In many cases, problems like those listed above can often cause starting issues. If none of these reasons seem relevant to you, then try getting your car towed to an auto mechanic for further inspection.

How Can You Determine If A Battery Is Positive Or Negative If It Isn’t Marked?

Unmarked car battery terminals are often problematic in that there is no indication of which terminal is positive and which is negative. The most accurate method to determine which terminal is positive and which negative is by using a VOM (Volt-Ohm Meter). The reason for doing so, when we start working with electricity, be it DC or AC, it’s a very important step that one should never skip.

After identifying positive and negative leads on an unmarked battery, connect the appropriate wire to its respective post. Although it can become confusing at times and frustration might get in your way from time to time, determining which unmarked car battery terminal is positive and which one is negative will only take you a few seconds.

All you need to do is apply some basic math knowledge. Remembering how basic electrical circuits work will also help you answer questions like how can you tell if an unmarked battery is positive or negative? More easily, a 12-volt system works with two batteries connected in series, which means that each battery supplies 6 volts of power for a total of 12 volts.

So if we have an unmarked car battery terminal with wires attached to it, chances are that one wire has been connected to a positive post and another wire has been connected to a negative post. If we were working with four batteries connected in series, then each battery would supply 3 volts for a total of 12 volts again.

In other words, when we’re dealing with unmarked car battery terminals there’s always one wire connected to a positive terminal and another wire connected to a negative terminal. So all you need to do is count how many posts are on your battery, add up their voltage ratings (6+6=12) and determine whether they match up with what you know about electricity in general.

What Occurs When A Negative Battery Terminal Is Connected To A Positive Battery Terminal?

Electricity travels from negative to positive, so when you connect a negative terminal to a positive terminal, electricity flows through your vehicle and back into your battery. This is called a short circuit and it could cause serious damage to all of your vehicle’s electrical components.

Always follow the correct procedure when jumpstarting a car. If your battery terminals are marked with + and – signs, then connecting them in that order will help ensure that you don’t accidentally create a short circuit.

The safest way to determine which terminal is which is by using a voltmeter or multimeter. Connect one lead of your meter to each terminal on your battery and read the voltage listed on your meter. Use caution when testing your battery as you may get shocked if both terminals are connected at once. Your goal should be to test only one terminal at a time while keeping other terminals unconnected.

Checking car battery voltage by voltmeter.

Testing either positive or negative first is up to you; some people prefer doing it in that order because they feel like they have more control over what happens next. Once you have tested both sides of your battery make sure you put everything back together correctly and safely. When possible, avoid creating a short circuit when working with any kind of electronics. Short circuits can damage wires and break circuits inside sensitive devices.

It’s important to know how to identify unmarked battery cables so you can take steps to prevent problems before they occur. For example, if you need new cables for your car, ask an auto parts store employee for assistance before buying anything. Having someone check whether your cables are properly labeled before you buy can save time and money in the long run.

How To Jumpstart A Car?

Jumpstarting a car may seem like a daunting task, but with these simple steps, you can be on your way in no time. Be aware that every vehicle’s battery cables are different, so if you’re jumpstarting a vehicle other than your own make sure to check out your owner’s manual for instructions.

Never attempt to jumpstart a frozen or recently discharged battery, as there is a risk of explosion or fire. Also, always wear safety glasses and gloves when working around batteries. A spark could cause them to explode. If you don’t have safety glasses and gloves, keep an eye out for damaged areas where sparks could occur – don’t let your skin come into contact with any sharp edges.

Finally, keep all ignition sources away from batteries while they are being charged; i.e. do not start or drive a vehicle while it is connected to another battery – this includes cell phones! Safety first! When all else fails just call AAA; they know what they’re doing! Good luck!

1.     Turn off both vehicles.

2.    Locate your positive (+) and negative (-) terminals. In most cases, red wires are positive and black wires are negative (red = power/positive/male; black = ground/negative/female).

3.      Place jumper cables directly over one another, then attach one end to each terminal (positive to positive, negative to negative).

4.       Start your donor vehicle and allow it to run for several minutes before attempting to start your disabled vehicle.

Starting car engine with jumper cables connected with another vehicle.


If you’re still having trouble determining which terminals are positive and negative, it might be time to have your car battery tested. Your mechanic can test your battery to make sure it’s in good condition and will hold a charge. If your battery is dead, you may need a new one or a jumpstart to get back on track. If you have any questions about identifying unmarked car battery terminals, contact us here at AAA. We can help!


Identify unmarked car battery terminals with a simple test. Unmarked battery cables can be scary to deal with, but if you follow a few safety steps, it’s easy. This guide will teach you how to tell which terminal is positive and which is negative, how to jumpstart a car, and how to test your car battery utilizing basic items that you most likely already have in your garage.

Any questions? Leave a comment!

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About Matthew Webb

Hi, I am Matthew! I am a dedicated car nerd! During the day, I am a journalist, at night I enjoy working on my 2 project cars. I have been a car nerd all my life, and am excited to share my knowledge with you!

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