Car Battery Terminals Crossed – What Happens If You Put The Battery Cables…

Car Battery Terminals Crossed – What Happens If You Put The Battery Cables On Wrong Sides

Automotive batteries can discharge for a host of different reasons, maybe you left the electricals on without the engine running, maybe it’s a parasitic drain eating away your charge, or maybe it’s just that, you don’t drive your vehicle as much – that can do it too.

In any case, if you cant get your car up, jump-starting the battery is a tried and tested solution that you might consider.

Jump starting a vehicle seems like an easy job, you just clamp the connectors and transfer the charge from the good battery to the dead one.

But as simple as it may seem, just the simple mistake of not connecting the terminals right can spell the end for your car battery.

Failing to recognize which is the positive and which negative is not a common occurrence, in fact, most people do actually have it right. But for the curiosity of the reader let’s consider what would happen if the terminals were reversed.

Risks Of Using Jumper Cables In Reverse

Car batteries are a bit more complex than they might appear. When jump-starting a car there are certain caveats to charging your vehicle as the transfer of energy from one battery to another is not as simple as it seems.

Connecting the battery terminals in reverse can cause serious damage to the battery itself, the electrical components, and even to yourself. Each terminal of a car battery uses 12V of current with positive and negative orientation. The cable on the positive terminal uses 12V while the one on the negative side uses.12V.

If the positives and negatives are switched, the battery will try to compensate and make the negative 12 volts into a positive charge resulting in a huge surge of power and an enormous amount of heat to be produced. Needless to say, it will not be tolerated well by the system or the components within and depending on certain factors will incur damage that is mostly going to be severe and irreparable.

Damage To Jumper Cables

With an instant surge of electricity, the first to face the wrath and the consequence of an experiment would the jumper cables. the extreme heat produced will quickly melt the insulators on the jumper cables, clamping them forever on the battery which will be next in line as the plastic top will melt and bend.

Damage To Car Battery

The battery will be warped as the acidic fluids inside will boil from the extreme heat produced in the reaction. Additionally, it may spill to damage parts in the vicinity and you might not be able to do anything about it.

Blown Fuse/Fusible Links

Whether you have an explosion or not depending on the other factors and the condition of the batteries, you will however surely find blown-up fuses and wires in your vehicle.

Damage To Alternator

The vehicle charging the bad battery might also suffer mechanical damage. The surge in power will have a negative effect on the alternator and may even cause irreparable harm.

Physical Damage

If the battery is in poor condition or has not been used in a while, jump-starting with cables reversed can worsen the situation. The bad battery can even explode and cause damage to the people around.

Other Things To Consider When Jump Starting

Firstly look in the owner’s manual for any precautions or know-hows before attempting to jump-start. Some cars may use lugs instead of clamps while some vehicle may require certain precautions as removing fuses or turning on defroster. Some newer cars do not allow jump-starting and can even void your warranty so be sure to read the warranty conditions as well.

Do not let the two vehicles touch

Turn both vehicles off before locating the battery

Make sure the terminals aren’t dirty and if they are clean them with a dry cloth.

Verify if the voltage is correct using a multimeter, if the voltages do not match it could spell serious problems for both the batteries.

Remove or turn off accessories and electricals such as headlights, radios, and turn signals as the surge in power will surely short them out

Make sure the vehicle are in neutral.

Check if the fluids aren’t frozen or the battery isn’t warped and bent out of shape. If it is, it could lead to an explosion.

Always start with the bad battery first as it does not have a charge and is safe to operate.

Don’t leave anything under the hood when starting the vehicle

After charging the battery, drive the car for 15-20 minutes to let the alternator fully charge the battery.

How To Connect Jumper Cables Properly

With the potential risk of physical harm and the enormous costs involved in replacing and reprogramming the ECUs, operating a car battery to jump-start without proper knowledge is not a good idea and can land you heavy repairs if you are not careful with the steps.

A car battery has two terminals namely positive and negative. Each terminal can be identified using its color and the sign it uses. Connecting each terminal firmly is extremely important as a loose connection can hinder the process and not effectively charge the battery.

Now with the basics out of the way, let’s get to the very important matter that requires you to be extremely careful and a little on guard.

In electronics, the positive terminal is always connected first in order to avoid a high voltage meet of the semiconductors. When connecting the jumper cables always remember to first clamp cables from the positive terminal of the battery, which is usually red in color and is marked by a positive sign, and only after properly connecting should you begin to connect the cables from the negative terminal, usually represented in black color with a minus (-) sign. Also, be wary of any metal object touching both terminals of the battery simultaneously.

To better understand the implications of not connecting the positive first, let us assume, one has connected the positive terminal first.

When the negative terminal is connected, the whole chassis including the metal bolts holding it in place become grounded, upon which placing the positive terminal, connects the spanner with any common ground resulting in some sparks, splashes in a best-case scenario, and a dead battery or even an explosion of the unit in a nightmarish one.

Connecting the positive terminal first is recommended to ensure the spanner is not able to cause any damage even if it has met the chassis.

On the contrary, it is recommended to start with the negative terminal while disconnecting the cables.

Can Get Electrocuted While Operating A Car Battery?

The current from a 12VDC system is not massive enough that it can harm you, in fact, one might not even be able to detect such low voltages as the current needs to overcome the resistance of and go through. To have any effect on you, the current from the battery will have to penetrate the skin in order to electrocute you.

High voltage sources of current independently are not dangerous, Although there are a few other things that you should look out for when dealing with your car battery such as an acid leak, sparks plug arcing, jumper cables.

How To Tell Which Is Positive And Negative On A Car Battery?

Don’t know which is positive and negative terminal on a car battery? This guide will show you how to identify them in just a few simple steps.

Learning how to jump-start a dead battery is critical for all car owners. To learn this, you must first know how to tell the positive and negative terminals on a car battery. If you aren’t used to working with the car battery, the two can be confusing.

In this guide, I show you how to differentiate between the positive and negative terminals on the car battery. I will also show you the right way to connect jumper cables when the battery is dead.

How to Tell Positive and Negative Terminals on a Car Battery?

To determine which is the positive and which is the negative battery terminal, you can take a look at the terminals. The positive battery terminal is usually colored red and has a plus sign posted on the cover. The negative may be colored black and have a minus (-) sign on the cover.

You might also tell by looking at the color-coded wires heading to the terminal. Here is some more detailed information on how to tell the battery terminals apart.

What is the Positive Terminal on a Car Battery?

The positive terminal cover on the battery is usually red-colored. However, not all car manufacturers use this method. If the terminals aren’t color-coded, you can also look at the cover to see if there’s a plus sign on it.

So, what do you do if the cover is missing? You are going to have to figure out the terminals another way. With some vehicles, the wires leading to the terminal will also be colored red, helping you to differentiate between the two.

I always recommend using a multimeter to be 100% sure which battery terminal is negative and which is positive.

What is the Negative Terminal on a Car Battery?

The negative terminal on the battery is sometimes black. However, if none of the terminals are red but both are black, this can make the process very confusing for you.

In this case, you need to look and see if there is a minus (-) sign printed on the battery cover. If so, this sign indicates that you have found the negative terminal of the battery.

The wiring insulator should also be black, with the positive side in red. This wiring is connected directly to the metal chassis of your vehicle, whereas the positive side would not be.

Right Way to Use Jumper Cables

While it’s easy to jump start a vehicle with a set of cables, there are some precautions that must be taken. If you mix up your jumper cable connectors or you touch the two ends together, you could end up injured, or cause damage to your car. For this reason, it’s wise to understand the steps before proceeding. I also recommend wearing protective gloves and a pair of safety glasses.

Here are some basic steps to follow, but you can get more detail by reading through your car’s service manual.

  • Attach the positive jumper cable to the positive terminal on your dead battery.
  • Attach the other positive jumper cable end to the positive terminal on the good battery
  • Attach a negative jumper cable end to the negative terminal on your good battery.
  • Put the opposite end of the negative jumper cable to a ground location on the car that has the dead battery. You should look for any bare metal part that is heavy-duty. It can be on the engine or connected to the chassis of the vehicle. All of these create a good ground connection. You don’t want to place your negative jumper cable end to the negative terminal on the dead battery. If you do, sparks could ignite the fumes coming out of the battery.
  • Double-check all of the connections before moving forward. It’s important that everything is secure.
  • Start up the car that has the good battery.
  • Rev the engine of the good car until RPMs hit 1,500 to 2,000. Keep up this engine speed for a few minutes.
  • Try to start the vehicle that has a dead battery. It could take a couple of tries to get it started.
  • Once you get the engine running, disconnect the ground connection that uses the negative jumper cable.
  • You can also remove both the negative and positive cable ends from the vehicle that had the good battery.
  • Finally, take the positive cable end off of the vehicle that had the dead battery.

It’s important that you don’t turn off your car engine for at least thirty minutes. The good battery only provided a minimal charge to the dead battery. If you shut off the car, you will be facing the same situation over again. Instead, allow the alternator to fully charge the battery. It’s best if you can take the vehicle for a drive down the highway to get the alternator working faster.

What Happens if Battery Cables are Hooked Up Backwards?

With the jumper cable polarity altered, there’s a big difference in the electrical current that’s flowing to each. It’s possible to melt the cables or cause a car fire because of the difference. For this reason alone, it’s very important that you always hook up the battery cables the right way.

The good news is that automakers realized this was a common problem for people that don’t understand car batteries. Therefore, many manufacturers install a main fuse that will blow before these problems occur. The best case scenario is that you blow the main fuse by hooking the terminals up wrong. If that’s the case, you can simply reverse the cables and replace the main fuse to get back on the road.

Frequently Asked Questions

Is the positive terminal on the left or right?

There is no way to tell if the positive or negative terminal is on the left or right. To find out, you need to look for a or – sign on the battery, or look at the colors of the cables. However, the most reliable way is to check with a multimeter.

How can I tell positive and negative on a car battery without color?

If there is no color, you can look for a or – sign on the car battery. A sign means it is the positive terminal, and – means negative. Other than that, the best way to determine what is positive and negative is to use a multimeter.

battery, terminals, crossed, happens

How do you tell positive and negative on an unmarked car battery?

If your car battery is not marked with a sign for the positive or negative terminal, the best way to find out is to measure it with a multimeter. Connect the DC multimeter clamps to both terminals and if the number starts with a “-” sign, it’s the other way around.

How can you tell which wire is positive and negative when black?

If both cables to the car battery are black, try looking for a or – sign on the car battery. If you can’t find these marks, you need to measure it with a multimeter or some other reliable method.

Did you know that you have to clean dirty car battery terminals routinely? If you don’t, even the best car battery won’t last very long.

You always go through your spring car cleaning checklist and take great care of your Alcantara or leather seats. You get your brake pads replaced as soon as you hear that dreaded screech at stop signs. You even put part of every paycheck into an “emergency car repair” fund, just in case life has it out for you. For all intents and purposes, you’re an excellent car owner who’s on top of everything.

If you haven’t been keeping up with auto battery maintenance—namely, cleaning car battery corrosion, that disgusting white/green crust seen on terminals—you’re not doing yourself any favors. Routine terminal scrubs can extend the life of your vehicle’s battery by years, saving you hundreds of dollars on a replacement and, perhaps most important of all, ensuring you get to work on time.

Luckily, car battery cleaning is fairly easy if you’re handy with a wrench. Here’s everything you need to know before getting started. (Or you can visit an auto battery service center near you for affordable testing, cleaning and general vehicle maintenance.)

Safety First!

It’s important to note that car battery corrosion is harmful to skin and eyes. You should always wear appropriate equipment, such as heavy-duty gloves and safety glasses, when dealing with automotive battery leaks or corroded terminals.

If any corrosive material gets on your skin or clothing, wash it off right away to prevent chemical burns and stains.

While the battery is still connected, do your best not to touch any other metal objects when working on the battery. Doing so increases the risk of shorting the battery.

Materials Needed

  • Protective gloves (rubber or latex)
  • Eye protection
  • Long-sleeved shirt and pants
  • Baking soda
  • Water (distilled preferably)
  • Old toothbrush, stiff-bristled wire brush or battery terminal cleaning tool
  • Dirty rags or towels
  • Petroleum jelly, dielectric grease or battery terminal protector
  • New anti-corrosion pads
  • Battery terminal cleaning spray
  • Wrench or socket set (10mm is the standard size for batteries)


Watch the tutorial video below, or follow our step-by-step directions for cleaning a car battery from start to finish.

Prepare Protect Yourself

Gather all your materials and put on your gloves, glasses and proper clothing.

Disconnect the Battery Cables

With your vehicle turned off—and the key out of the ignition—pop the hood, lift the plastic or rubber terminal covers and disconnect your battery cables from the battery posts.

Always begin with the negative (-) cable first! This is usually identifiable by its black cable. Then disconnect the positive cable, which is often marked by a red cable. (Once finished, you will reconnect these in reverse order.)

If the corrosion is extreme, you may need to use some elbow grease and wiggle the connectors off the battery terminals. A special battery terminal puller may be required if the corrosion is especially bad.

While you’re at it, inspect the terminals, cables, posts and battery itself for signs of damage. Swollen, cracked or bulging batteries should be replaced, as should any fraying cables or rusted connectors.

Clean Terminals with Baking Soda and Water

Your goal here is to neutralize battery acid with a mixture of baking soda and water. (Battery terminal cleaner spray can also be used in lieu of baking soda and water.)

Pour about a tablespoon of baking soda directly on the corroded battery terminal. Don’t be shy; if you need more baking soda, you need more baking soda.

Next, pour a little bit of distilled water over the baking soda. It should begin bubbling or fizzing, which indicates that your battery corrosion is acid. Hot water is also a good idea, especially for stubborn built-up gunk on battery posts.

Using a wet toothbrush, wire brush or terminal cleaning tool, scrub everything.

Repeat these steps until there is no more visible corrosion and the baking soda-water mixture no longer fizzes.

Rinse and wipe away with a clean rag or towel, then allow the battery to dry thoroughly.

Clean Connectors

Perform the same cleaning steps above on the loose battery cable terminals.

Again, let everything dry before reconnecting the battery to the vehicle. You don’t want to mix water with electricity… that would be bad.


Before reconnecting any cables, perform all your preventative tasks.

Wipe the terminals, clamps and exposed metal connectors with dielectric grease or petroleum jelly. This will help slow down the buildup of corrosion.

Install new anti-corrosion terminal pads. These will be placed over the terminals, in between the battery and connectors.

Reconnect Cables

Install the battery cables in reverse order, starting with the positive connector and clamp, followed by the negative (-). Tighten with a wrench or socket.

As an additional layer of protection, coat terminal protector spray over the terminals and clamps. Try to keep from over spraying onto other components.

Finally—and most importantly—pat yourself on the back for a job well done!

What Causes Car Battery Corrosion

Every vehicle battery will eventually build up that white powder or green/blue crust—this is 100% normal. As your battery runs, the sulfuric acid inside releases hydrogen gas through vents, which then reacts with air, moisture and even salt.

The most common causes of automotive battery corrosion include:


Wondering how long a car battery should last? Most batteries are warrantied for 3 years, but modern automotive battery packs can sometimes last for 5 years, provided they’re properly maintained. Once batteries begin dying, cleaning corroded terminals won’t always solve the problem; you’ll want to find the best place to buy a car battery near you and have it replaced.


Corrosion can speed up if the environment is moist and/or humid, and if the vehicle is exposed to lots of road salt or salty air. You’ll know you’re in such an atmosphere if the corrosion is green or blue, typically.


Battery acid can leak at a faster pace if your battery has developed any cracks, bulges or significant damage.

Overcharging Undercharging

If your battery is constantly being overcharged, the fluid inside expands and can leak out onto terminals.

Excess corrosion on the positive terminal is a sign of overcharging, which can be caused by a faulty voltage regulator, so check with your auto service center for assistance.

Excess corrosion on the negative terminal is a sign of undercharging, which can happen if your vehicle isn’t being driven enough or if you have extra onboard electronics drawing too much battery power.


Battery corrosion can occur all year, though it’s more likely to cause problems during hot summers.

How Often to Clean Battery Terminals

You should try to perform battery terminal cleaning any time there is visible corrosion. Of course, not all of us have the time to check for battery post corrosion regularly, so aim for once or twice per year. Your auto service center technicians or mechanics can perform this task for you, as well.

To prevent battery corrosion in the future, keep up with maintenance and never buy the cheapest car battery when the time comes for a replacement! Seals around these cheap auto batteries are poor, allowing more hydrogen gas to leak and leave deposits on battery posts, ultimately reducing their lifespan dramatically.

Visit our car battery store and Nissan service center near Kansas City for a battery check, diagnosis and replacement, if needed. We carry many of the best car battery brands, including Nissan-authorized batteries, and can easily order and install the right type for your vehicle. Contact McCarthy Nissan at (913) 324-7364 to speak with a member of our team and schedule an appointment.

Unmarked Car Battery Terminals (Beginners Guide With Pictures)

Car batteries, without them, we’re going nowhere; knowing which terminal is which can be a head-scratcher, but five minutes from now, you’ll be an expert.

Car battery terminals will be marked and color-coded. The color red and the plus sign for the positive terminal, and the color black and the minus sign for the negative terminal. The negative terminal connects to the vehicle’s metal chassis.

In this post, I’ll show you clearly which terminal is which, how to fit a battery, and what to do if you connect it back ways. You’ll also learn how to Jumpstart your car.

If your battery is flat and you are locked out of your car, check out the secret fix here.

How Can You Tell Which Terminal Is Which?

The negative terminal is color-coded black and will be connected to the minus side of the battery.

The minus will be stamped into the battery plastic casing; you may need to look closely. The negative terminal may or may not have a plastic cover over the terminal connector.

The negative wiring insulator will be colored black, and the negative terminal attaches directly to the negative side of the battery and to the metal chassis of the car.

If you have ever wondered what the difference is between ground and negative, then this post is for you –“Is ground and negative the same?”

The positive terminal is colored red and will be connected to the plus side of the battery.

The plus sign will be stamped into the plastic battery casing, it may be difficult to spot at first, but it is there.

The positive terminal will likely have a red plastic cover shielding the terminal; it will likely also be marked with a plus sign. The positive wiring insulator will be colored red.

Battery negative identified by a minus sign and black insulator as highlighted above

How To Test A Car Battery?

Battery failure is common, but so too is assuming a flat battery means your battery is faulty. Misdiagnosing a battery can be an expensive mistake.

Checking battery voltage as per the above picture is OK, but a battery that shows a full 12.65 volts could still be faulty. The only way to be sure is to test the battery under load.

The process is simple, but you’ll need a helper and a DVOM (voltmeter). The graphic shows the process, but you’ll need to start the test with a fully charged battery. This test won’t work if the battery is flat.

Step 1 – Charge battery to 12.65 voltsStep 2 – Set the voltmeter to 20v DCStep 3 – Connect the voltmeter as per the graphic aboveStep 4 – Have the helper crank engineStep 5 – A reading on the voltmeter below 9 volts indicates a faulty battery.

If you find your battery has failed, check out the battery blog section, where we cover a ton of battery-buying options.

How To Replace A Car Battery

A car battery will have a fastener on each terminal and a third fastener; the battery hold down, and it secures the battery to the chassis of the car.

Mistakes to avoid:

But before removing any terminals, you should check your driver’s manual; some cars may require calibrating of Windows and steering, and some will need a throttle to relearn, which may require a trip to the shop. I wrote a whole post about recalibrating – Car won’t idle after dead battery.

The more sophisticated the car, the more likely disconnecting the battery will cause issues.

You can avoid all these potential issues by using KAM (Keep Alive Memory); it’s a simple device that keeps power in the car while the battery is removed.

The Schumacher memory saver tool is great, easy to use, pay for itself with just a single use, and is conveniently available on

Step 1: Plug in your KAM device if needed.Step 2: Now we’re ready to change the battery, remove the battery hold-down bolt; it will likely be one bolt at the base of the batteryStep 3: Remove the black, negative, minus terminal firstStep 4: Now remove the red, positive, plus terminalStep 5: Remove the old and fit the new batteryStep 6: Fit the red, positive battery terminalStep 7: Fit the black, negative battery terminalStep 8: Secure the battery with the hold-down bracket

You should note that modern cars employ a battery control module that requires coding to the new battery. A scan tool is required to code the battery to control the module. Your vehicle will still operate without coding the battery, but it will shorten the battery life.

Anyway, it’s all covered in the post I wrote about fitting a car battery, including pictures, and you can check it out here “How hard to fit car battery.”

How To Jumpstart A Car

You’ll need a donor vehicle or a spare battery or alternatively, consider buying a jump pack. The little NOCO boost pack is about the best I’ve seen, and I’ve been a mechanic for over twenty-five years.

It’s small enough to fit in a glove box and powerful enough to start a diesel engine. Anyway, you can check it out here on the Auto electrical tools page.

To jump it with a regular set of jumpers, follow these steps.

Donor car or any fully charged 12-volt battery, the jump-starting procedure is simple. Red positive to red positive booster cable first, then connect the negative black (-) to both battery and chassis or engine ground. A ground is any bare metal on the chassis or engine.

Check the battery and verify both negative and positive markings before connecting terminals.

Step 1:

Move a donor car close enough to connect booster cables.

Step 2:

Put the jumper cables on in sequences 1, 2, 3, and 4.

Step 3:

Start the donor car and leave it idling.

Step 4:

Now start your car and leave the cables attached and your car idling for a few minutes before removing them.

Step 5:

Now with the engine running, remove the jumpers in reverse order 4, 3, 2, and 1. Once running, your car’s alternator will charge the battery back up again; if you wondering how long and want a few tips to help charge it up faster, then check out this post, “How long to charge a battery driving?”

We are assuming; of course, all is OK in alternator land. If you think it might not be, check out this post; we cover alternator testing, and we cover replacing alternators here – “Hard to change alternator?”

Hooked Up Battery Cables Backwards

This is a common enough problem, as is hooking up jumper cables the wrong way. Don’t panic; we’ll figure it out!

Your symptoms could range from:

  • No power at all, anywhere
  • Ignition lights work, but the engine won’t crank
  • Car cranks but won’t start
  • Electrical gremlins since the wrong battery hookup

Hooking the cables up backward will usually blow the main fuse. Fuses are fitted in the under-hood fuse box, interior fuse box, and possibly a trunk fuse box.

First, locate your handbook or Google where your fuse boxes are, and you’ll also need to know the individual fuse locations.

If you have no power at all, anywhere, first verify that your battery is OK. You can check it with a voltmeter (12.65v is full) or using booster cables from a fully charged 12v battery; use the jump-starting guide above.

You can find a simple handheld battery tester listed here on the “Auto electrical repair tools page.”

If the battery checks out, then go ahead and check the fuses.

A blown fuse will have a broken element visible through the plastic body. A tweezers tool fitted to the inside fuse box cover will help with removal. Your fuses may not look identical to those shown here, but you get the idea.

Look for the following fuses; you won’t have all of these but check whichever ones you’ve got.

  • Main fuse
  • Battery monitoring fuse
  • ECU/ECM/PCM fuse
  • CEM fuse
  • Instrument panel fuse
  • Car fuse bank

If your ignition lights work, but the engine won’t crank, check the following fuses:

  • Main fuse
  • Anti-theft fuse
  • Immobilizer fuse
  • ECU/ECM/PCM fuse
  • Starter motor relay/fuse
  • Ignition fuse

If none of this helped, check out this post; it covers all the fixes for mixing up the terminals – “Battery sparked now won’t start.”

Check out this post also; it covers fault finding a no crank “Car won’t start clicking noise”

Fuse types and color chart.

If your car cranks but won’t start, check the following fuses:

  • Main fuse
  • Anti-theft fuse
  • Immobilizer fuse
  • Ecu/Ecm/Pcm fuse
  • Ignition coil fuse
  • Fuel pump fuse
  • Fuel injector fuse

The battery can drain for a ton of reasons; as you know, battery failure is the most common cause, but a short in the wiring system can drain your battery too. A persistent unexplained drain points to a short so long as your alternator and battery tested OK. I cover testing both battery and alternator here in this post, “Car battery drain”

If you think you have a wiring short you can check out my beginner’s guide to finding a short right here.

Having a workshop manual for your vehicle is always a good plan; they only cost a few dollars but will save you a packet. A good manual will cover your vehicle in detail, including repair and replacement procedures, electrical wiring diagrams, system overview, troubleshooting section, fastener torque specs, etc., all mission-critical info.

You may find the following links helpful:

Related Questions

Which terminal is ground on a car battery? The ground terminal is the black minus terminal on the battery, also known as the negative or ground terminal. It connects the vehicle chassis to the minus side of the battery.

John Cunningham is an Automotive Technician and writer on He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.

John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.

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.

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.
battery, terminals, crossed, happens

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.

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!

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).

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

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

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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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