What is battery polarity and how to determine it

What is the polarity of the car battery and how to determine it?

When choosing a battery, it is necessary to pay attention to a number of parameters. Among the main ones, it is worth noting the nominal capacity, body size, starter current and polarity. Today we will talk about the polarity of the car battery and how to determine it. This is one of the key parameters of the battery. If you choose the wrong polarity you simply will not be able to connect the battery on your car and start using it.

Why is it necessary to know the polarity of the car battery?

Polarity is a characteristic of a car battery that determines the location of its external leads. If you buy a car battery with the wrong polarity, you will get a problem with its installation and connection.

The fact is that the planting recess under the battery allows you to install it in one position. If the polarity will be wrong, then the length of wires with terminals will simply not be long enough to connect them to the appropriate pins of the battery. That is, you simply won’t be able to operate the battery.

How to determine the polarity of the car battery

Of course, you can engage in lengthening the appropriate wires and “win” the situation. But, think, do you need unnecessary problems and making all sorts of additional “crutches”? In such a situation you are likely to go back to the store or go to an online store to replace the battery with a model of the required polarity. In these cases, the sellers are accommodating, and the battery can be exchanged. But in order not to lose precious time and not to waste nerves, you need to be able to choose the required polarity at once. Let’s figure out how to do it.

Types of battery polarity

Manufacturers produce batteries with six types of polarity. They differ in the layout and association of the elements of the battery with each other. Four types of polarity are the most common. Two types are used for passenger car batteries and two are used for truck batteries.

Car Batteries

Before you determine the polarity of a car battery, turn the battery toward you with the front (with the sticker on). The battery terminals will be on the top side of the battery on the side closest to you. Now look at the location of the positive (+) and negative (leads) on the battery. There are two possibilities:

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1) The positive current lead is on the right and the negative lead is on the left. This is reversed polarity or European polarity. This is also referred to as the “0” polarity. The image below shows the top view of the car battery.

Reverse polarity of the car battery

Reverse polarity of the car battery

2) The positive terminal is on the left and the negative terminal is on the right. This is the forward polarity of the car battery, or Russian polarity. This type of polarity is also referred to as “1”. Below you can see a top view of the battery with direct polarity.

Direct polarity of the car battery

Direct polarity of the car battery

It is also worth mentioning the mythical “Asian” and “American” polarities. They do not exist in nature. There are Asian and American size batteries. Asian-type batteries are slightly less wide than European batteries and slightly taller. They also don’t have a “step” on the top cover. The terminals of Asian batteries may be thinner, and in some cases are made for different mountings.

The American type battery differs in the type of current leads and their location. The terminals are not on the top plane, but on the side. They are made for bolt mounting. Although there are models with terminals both on the side surface and standard on the top cover.

Asian size

American size

As far as polarity is concerned, Asian batteries have it reversed or “0” and American batteries have it straight or “1”. Return to content

Truck batteries

Most truck batteries have current leads on one of the short sides of the battery. To determine the polarity of a truck battery, turn the battery toward you with the side with the leads and look at their location. There are two possibilities here as well:

1) The positive terminal is on the left and the negative terminal is on the right. This is the reverse or European polarity of the car battery. This is indicated by the number “3”.

Reverse polarity for truck battery

Reverse polarity of the truck battery

2) The positive terminal is on the right and the negative terminal is on the left. This is the polarity of the car battery straight or Russian. It is indicated by the number “4”.

Reverse truck battery polarity

Straight polarity of a truck battery

Truck batteries may be encountered with an arrangement denoted by the number “2”. In this case, the battery terminals are positioned diagonally on the top side of the battery.

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Diagonal pin assignment

Diagonal terminal layout

Other types of polarity

There are two other, less common types of battery layouts which are indicated by the numbers “6” and “9”. They are shown in the pictures below.

Polarity 6

Polarity 9

How do you determine the polarity if the battery terminals are not labeled?

There are times when you need to determine the polarity of car batteries that do not have current lead markings on them. As a rule, this problem does not exist, because the battery manufacturers distinguish the terminals with “+” and “-” signs. Often they are additionally marked with colors. The positive is red and the negative is black or blue. But let’s assume that there is no marking. What to do then?

Here are 4 different ways to determine the polarity of the leads:

  • The diameter of the current leads. The easiest option is to measure the diameter of the battery leads. Positive leads always have a larger diameter than negative leads. To be more precise, in the European size the positive terminal has a diameter of 19.5 mm, while the negative terminal has a diameter of 17.9 mm. For Asian batteries these values are 12.7 and 11.1 millimeters. A caliper can be used to measure the diameter;
  • Citric Acid. In principle, you can take a weak solution of any other acid. Screw the copper wires to the battery terminals, and dip the other ends of the bare wires into the acid solution. They should not touch each other. Where there is a rapid outgassing, there is a minus current lead;
  • Raw potatoes. In this case, the copper wires are poked into the cut of the potato. The distance between them is 5 to 10 millimeters. Around the wire from the positive lead, the potato will turn green;
  • Multimeter. Take a multimeter and turn it on to measure the voltage. Use the stylus to touch the battery terminals and look at the readings. If the voltage is positive, you have a “+” lead under the red probe and a “-” lead under the black one. If the voltage is negative, it is the other way around. Under the red dipstick you have “-” and under the black dipstick you have “+”.

Now you know how to determine the polarity of the car battery yourself. If you still have questions, ask them in the comments. And don’t hesitate to ask the consultants in stores about the characteristics of the battery. They have to know them all and advise you. Have a nice shopping experience! Back to content

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How to determine the polarity of the battery: European or Russian? Tips and tricks

There is one characteristic that is very important when choosing a battery model – its polarity, i.e. the location of external current outputs (current output “+” and “-“) on the front panels of the battery.

When you need a new battery for your car and you come to the store, the salesperson will definitely ask you, “Do you want to know the polarity of the battery on your car?” And that’s where you’re bound to get confused. First, for many people the definition of “polarity” will be unknown. Secondly, few people remember which side is the “plus” and “minus” on the battery of their car. Thirdly, few people know how to correctly determine the polarity of the battery: what side to approach it from; how to turn it towards yourself; turn it around or turn it away. About all this you will learn further, as well as how to determine the polarity without any devices, applying folk tiphkahi.

How to determine battery polarity

What is polarity

The car battery is the primary source of power (secondary generator). It is a rechargeable device and has a number of technical characteristics, such as: housing size, nominal capacity, current and voltage magnitude. In addition to all of the above, no less important is such a parameter as polarity.

Polarity is the location of the two current-carrying elements of the battery: plus and minus. They are placed on the body so that the terminals of the power wires are connected to them without a shortage of length. After all, in order to save money, manufacturers calculate every millimeter of wire. Try turning the battery around and you’re unlikely to be able to slip the terminals onto the positive or negative terminal of the battery.

Types of polarity

The modern car market offers a wide group of different types of batteries for cars. There are classic acid batteries, alkaline batteries, gel batteries and others. But all car batteries work according to the same scheme. Therefore, they have only 2 current-carrying elements: positive and negative. Depending on the manufacturer, the “plus” and “minus” may be diametrically opposed. Therefore, there are two types of polarity:

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The first is often found on cars made in Russia, and the second on foreign cars from European countries.


Straight polarity is often called “Russian” because the arrangement of current output elements was developed back in the USSR and inherited by Russian manufacturers. The Russian polarity is defined as follows:

  • positive lead on the left;
  • negative – on the right.

This design of the battery is found on all LADA and UAZ models, even the latest modifications.

Reverse polarity

Reverse polarity (sales managers call it “European”) is defined by the following position:

  • positive lead on the right;
  • negative terminal on the left.

This type of battery is found on almost all models: Audi, Volkswagen, Mercedes-Benz, Volvo, Land Rover and others.

How to determine polarity

If you do not have a Russian or European car model, but, say, American, Japanese or Chinese, you can determine the polarity of the battery quite simply. To do this, stand in front of the car so that the battery “looks” with its terminals toward you. If the “-” is on the left and the “+” is on the right, it’s the reverse type. If it is the other way around, it is the forward type. The fact is that the battery can be placed on cars in different ways: with the terminals facing forward, backward or sideways. That’s why you should always stand in front of the battery so that it’s in front of you from the front. After all, if you look at the battery from behind, its polarity will be deceptively reversed for you.

What happens if you reverse polarity?

Even professional drivers can accidentally put the negative terminal on the positive terminal of the battery. As a rule, it happens in a hurry, for example, during an emergency repair of the car on the highway. At the same time, it will not be possible to tighten the terminal, because the terminals of the battery have different diameters: 19,5 mm (+) and 17,9 mm (-). Asian cars have something similar: 12,7 mm vs. 11,1 mm. However, even a momentary touch of different polarity contacts can deliver a lot of unpleasant consequences, such as:

  1. Blown relays and fuses.
  2. Exploding capacitors and diodes.
  3. Commutator burns out.
  4. Melting of wiring.
  5. Alarm problems occur.
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The electronic control unit (ECU) is damaged rarely, as modern cars have good protection against short circuits. But even the listed malfunctions are enough for a thorough concern, and sometimes for serious repair, for example, replacement of the commutator or alternator.

People’s tips: how to determine the polarity?

Imagine that you got a battery that has no marking of current output elements “+” and “-“, and they are not marked with colors, such as red / blue. You also don’t have a multimeter handy. What to do in this situation? What is the polarity on the battery? There are a few folk tiphacks that will help you identify the positive and negative terminals of the battery:

  1. Look at the current-carrying elements and identify among them the one that is larger. The thicker one is the “plus” and the thinner one is the “minus.” To be sure you can measure the diameter with a caliper: 19.5 mm “+” versus 17.9 mm “-” (Russian and European standards).
  2. Dissolve citric acid in a jar or beaker. Screw a thin wire onto each lead. Dip the bare wire ends in a container of acid, without letting them touch (close). The wire that will start the electrolysis of water and the release of hydrogen (noticeable bubbling) is the “minus” and the other is the “plus”.
  3. Take a raw potato, cut it in half and stick two wires connected to the battery into it. The distance between the contacts is 3 – 5 cm. After a few seconds the area of the potato around one contact of the wire will start to turn slightly green. This is the “plus.”

If such an alien unmarked battery is on the car, you can trace where the wires go: the plus wire goes to the alternator and starter, and the minus wire goes to the body.


Finding out the polarity of the battery is simple enough. Turn it toward you and find out from the “+”/”-” markings which side is the plus side and which side is the minus side. If there are no markings on the battery, use the folk tiphacks for diagnostics.

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