"Lighting" up a car is one of the surest ways to start the engine when the battery is dead and there is no start-charger nearby. However, this operation is associated with certain risks. Starting with the fact that you can be left with two discharged batteries, and ending with serious breakdowns of electrical equipment. There is no single correct and 100% safe way for all occasions. To properly "light" a car, you must: a) take into account several important factors; b) based on them, choose the safest algorithm of actions. What are these factors, what algorithms are there and which one to choose in each case is described in detail in the article.

10 reasons to stop "lighting"

Cases where a refusal to a request to "light" a car is due to the fact that a person by nature is not inclined to mutual assistance on the road, we will leave to psychologists. Our task is to analyze those possible situations where the unwillingness to help is quite justified. Read carefully the 10 points below and remember them for the future. If at least one of them is your case, then the refusal will be justified, and resentment will not follow.

Now a short list of reasons why you should not "light" a car:

  1. Uncertainty about whether it is possible to "light" a car.
  2. Mismatched voltage.
  3. Huge difference in battery capacity.
  4. An abundance of electronics.
  5. The battery of the donor car is barely breathing.
  6. Generator malfunctions.
  7. There are no normal wires.
  8. The car is easier to push.
  9. It is possible to reach the car to the charger.
  10. Ignorance of how to properly "light" a car.

For many motorists, all these things are elementary and understandable. But not for everyone. We must be sympathetic to those who bought a car to drive, and not to understand it. For these, each item is briefly discussed below.

Reason number 1. Uncertainty - is it possible to "light" a car

Uncertainty is a great reason not to light a car
Uncertainty is a great reason not to light a car

Among motorists, both in real life and on the Internet, there are many stories about how a generator, a voltage regulator relay, an ECU, and so on burned out after "lighting" up. That is, various problems that scare away even the thought of “risking the health” of your car in order to help the one that didn’t start today.

All these stories, unlike many others on the automotive theme, are not myths. This really happened. But these problems, so to speak, occur selectively. That is, not with every first. Nevertheless, the uncertainty whether it is possible to light a car has a right to exist. If at least one of the two of you has it (uncertainty), you should not light a car. Moreover, you can help in such a situation in other, more harmless ways.

Reason number 2. On-board voltage mismatch

This, it would seem, is elementary - if the voltage of the on-board network of one car is 12 V, and the other is 24 V, then lighting is out of the question. But no. Practice remembers many cases when they tried to light a 12-volt on-board network from a 24-volt one. Or vice versa. You can't do that! These are guaranteed problems.

Reason number 3. Significant difference between battery capacities

The capacity of car batteries is measured in ampere-hours. If it is written on a dead battery that it is 120-180 ampere-hours, then trying to light it from the battery for 50-60 ampere-hours is strongly not recommended. The energy reserve and maximum starting current of a smaller battery may simply not be enough to start a motor equipped with a battery twice as large. But on the contrary - you can safely. Most importantly, do not forget about stress.

Reason number 4. Electronics

There is a myth that a modern car stuffed with electronics cannot be lit. It's not made up out of thin air. There are many examples in life when entire control units burned out, not to mention fuses and other trifles. However, despite such cases, it is still a myth. Problems happened to those who did not know how to properly light a car. And taking into account the fact that there are several ways, it was chosen, for sure, far from the safest.

Reason number 5. Weak donor battery

These include all batteries that are more than 4-5 years old. They no longer have the capacity (and cold scrolling current) that is indicated on the case. Weak batteries should also be considered those that are operated on machines with faulty generators, relay-regulators, and low on-board voltage. It is very likely that in such cases the batteries are far from being fully charged, and therefore they themselves can be blown away before the lighting is successful.

Reason number 6. Generator malfunctions

If the battery charging system is faulty on the car, it is useless to light it
If the battery charging system is faulty on the car, it is useless to light it

If one of the two cars has a faulty battery charging system, lighting up is almost guaranteed to end in a fiasco. If your car is a donor, then you yourself may end up with a dead battery. Starting the car in this way with a faulty generator or voltage regulator relay is useless. Even if the engine can be started, it will not work for long.

Reason number 7. No special wires

No normal wires - do not light up the car!
No normal wires - do not light up the car!

Not all car owners carry them in the trunk. Simply because they monitor the state and level of charge of their battery, and they do not need wires. So. It is impossible to use any kind of wires in order to light a car. A large current will flow through them at the time of the starter operation. And this means that thin and dilapidated wires will simply burn out. This is at best. Much worse if the insulation melts and a short circuit occurs.

Reason number 8. The car is easier to revive with a pusher

If you can push, push!
If you can push, push!

There are still a lot of cars on domestic roads that can be started without problems using the good old method. From a pusher or from a tugboat. So, if it is possible to revive your car with a dead battery in this way, it is better to resort to it. And stop smoking. So much safer. Unfortunately, not every car can be started this way. As a rule, if the engine is not carburetor, not diesel, and the box is not automatic, you cannot start it from a tug.

Reason number 9. Can be reached for charger

Sometimes it's better to tug than to light up
Sometimes it's better to tug than to light up

If there is a tow rope and someone who wants to help, and your garage is not very far away, it is better to refuse to light a car. It is much easier and, most importantly, safer to take it in tow, drag it to a place where there is a charge, and revive the battery in a natural way. So you are guaranteed not to burn anything, and also you will not need to convince the one who stopped to help that lighting is absolutely safe in any case. Especially since it's not true.

Reason number 10. No understanding - how to properly light a car

The last reasonable reason why you should not even start lighting a car is the lack of knowledge of how it is done. It only seems simple at first glance - put on two wires and you're done. Further you will understand why there are only two wires for lighting a car, and there are 10 ways to light a car, and this is at least.

10 ways to light up a car

Why so much? The fact is that not every method of lighting is suitable for different situations. Therefore, the task is to understand, using the example of several different algorithms, how it works, and how to correctly light one car from another car. On the other hand, knowing several ways allows you to understand how some of them are not safe and not universal.

Conventions. To simplify the material in the following algorithms, the car from which you need to light up will be called "car A", and the one that needs to be started by lighting up "car B". All the parts needed in the process - batteries, generators, and so on - will be named accordingly. Selectively, some options are clearly shown in the diagrams.

Car lighting scheme
Car lighting scheme

Method number 1. Lighting up with the engine off A

Differs in simplicity and relative safety. The risk, of course, is present (as in all other options). However, this method can be considered the most preferable. Although it is not suitable for all cases. But more on that below.

Algorithm 1:

  1. Car A parks near B so that their batteries are as close as possible.
  2. Motor A stops.
  3. The terminals from the battery are not removed anywhere.
  4. Batteries A and B are connected by wires for lighting directly (“minus” not through “ground”, but directly to the terminals).
  5. Battery B is given 5-15 minutes to recharge from Battery A.
  6. Lighting wires are removed.
  7. The engine of car B starts.
Car lighting scheme No. 1
Car lighting scheme No. 1

Disadvantages of this method? First, you have to wait, while there are faster ways. Secondly, battery A can discharge itself. Thirdly, while connecting the wires for lighting to the on-board network of car B, a current surge may occur and disable the electronics that are in standby mode. Fourthly, the battery of car B may not be charged enough to spin the starter.

Now the advantages of this method. First, the procedure is 90% safe for car A. Second, there is a risk of damaging the electronics of car B, but it is much less than in many other algorithms.

Method number 2. With engine A off and car B's battery disconnected

This method is similar to the previous one, but with only one step difference. Suitable for cases where removing the terminal from the battery of car B is acceptable. It is better not to use in situations where problems may arise after disconnecting the terminal with machine B.

Algorithm 2:

  1. Car A parks next to B so that both batteries are closer.
  2. Engine A stops.
  3. The terminals are removed from the battery B (you can use one, any).
  4. Both batteries are connected by wires for lighting directly.
  5. Waiting 5-15 minutes.
  6. Lighting wires are removed.
  7. The battery of car B is connected to the on-board network.
  8. Car B's engine starts.

The disadvantages of this method are practically the same as in the first method. Except for one moment, which is now turning into an advantage. Namely, the procedure becomes 100% safe for the on-board network B.

Method number 3. " Castling"

Another method that has many advantages, but it is not suitable for all cases. To light a car in this way without problems, there should be no complications on A and B after completely disconnecting the batteries from the on-board networks. Such problems include, for example, resetting important settings of a particular electronics, floating idle. Accordingly, if both machines are not particularly stuffed with this electronics, the method should be considered the most preferable.

Algorithm 3:

  1. Both batteries are disconnected and removed from the vehicles.
  2. Battery A is connected to the on-board network of car B (you can use wires for lighting, if the batteries are of different sizes).
  3. Motor B starts from a live battery.
  4. Battery A is given some time to recharge from the generator of car B.
  5. When engine B is running, battery A is disconnected.
  6. Battery B is put in its place.
  7. Battery A is returned to your vehicle.
Scheme No. 3
Scheme No. 3

The advantages of this method are as follows. Firstly, the owner of machine A risks almost nothing. Secondly, there will be no current and voltage surges on machine B. There are also disadvantages. First - not every car owner will agree to disconnect the battery from the on-board network. The second - not always the engine B will continue to work after the battery is disconnected, provided for in paragraph 5 (a serviceable one should not stall).

Method number 4. Classic or old fashioned

This method of lighting a car can deservedly be called a classic of the genre. He is very efficient. But taking into account the features of modern cars, it is far from the best in terms of safety.

Algorithm 4:

  1. Car A parks next to B.
  2. Engine A stops.
  3. Batteries A and B are connected directly by cigarette lighter wires.
  4. Car A starts.
  5. Engine B starts.
  6. Lighting wires are removed.

The most significant drawback of the method is that there is a big risk of damaging the electronics of both cars. The first time this can happen is when a large surge of current and voltage goes from battery A to B. The second time, when generator B starts up, the surge can go to the on-board network of car A.

Most out of this method, you should heed just one important recommendation. After connecting the ignition wires and starting engine A, do not rush to start engine B. Give battery B some time to recharge from generator A. With this approach, current and voltage surges can be avoided, and the operation is almost completely safe for both cars.

Method number 5. With the connection of the "minus" through the "mass"


Scheme No. 5
Scheme No. 5

Algorithm of this differs from the previous method only in that the “minus” of battery A is connected by a wire for lighting not from terminal to terminal, but through “ground”. Some motorists believe that this nuance improves the safety of the procedure. In fact, there is no special meaning in such lighting. Its advantages and disadvantages are the same as those of the 4th method.

Method number 6. Second variation of the 5th

Scheme No. 6
Scheme No. 6

It is based on the same old-fashioned method and the opinion that lighting through the "mass" is safer. Only unlike the 5th algorithm, in this case, the negative terminal is removed only from battery B. While battery A remains connected to its on-board network. Again, the advantages and disadvantages do not change. However, if the owner of car A flatly refuses to disconnect the terminals from his battery, then this option can help convince him not to refuse help.

Method number 7. The most effective and dangerous

One of the most dangerous algorithms. Doing so is highly discouraged. As a matter of fact, most often those who are not familiar with other methods of lighting a car act in this way. It is clear that after such procedures the most problems arise, new myths and questions of the type are born - is it possible to light a car.

Algorithm 7 (extremely bad):

  1. Car A parks near B.
  2. Engine A, however, does not stop.
  3. Batteries are connected by wires for lighting.
  4. Engine B starts.
  5. Wires are removed.

If you have carefully read the previous algorithms, then you should have already noticed the most important drawback. It consists in the fact that at the moment the wires for lighting are connected, a voltage of 14.5 V will go into the on-board network B. This is despite the fact that the voltage of a discharged battery B can be less than 10 V. Due to such a skew, a voltage and current surge is provided. As for the benefits, there are few of them. The most significant thing is that there are a lot of chances to start motor B even under the most unfavorable conditions.

Method number 8. With disconnection of battery A "on the go"

Scheme number 8 - never do this!
Scheme number 8 - never do this!

Another method that captivates with its imaginary safety and efficiency. In terms of efficiency, it really is practically trouble-free. But in terms of security, it is very much inferior to the options described above. Therefore, no one here will recommend using it. You need to know about it only in case someone offers you to light a car using this method.

Algorithm 8 (on a note):

  1. Cars A and B are installed side by side.
  2. Engine A does not stop.
  3. Both terminals are removed from battery A “on the go”.
  4. Battery B is connected directly to the on-board network A using cigarette lighter wires.
  5. Engine B starts.
  6. Wires are removed.
  7. The battery of machine A is connected either “on the go” or after the engine has stopped.

Both car owners may face the disadvantages of this algorithm. For A, such actions may end in problems after the battery is reconnected. And for the on-board network B, this method threatens with a serious jump in voltage and current. There are no advantages that would 100% justify this method of lighting a car. Although, if you're lucky, then everything will work out. And quite effectively.

Method number 9. Recharging the battery from a donor generator

In conclusion, let's look at a couple more relatively safe ways to light a car from another car.

Algorithm 9 (one of the best):

  1. Machines are installed side by side.
  2. The clamps are not removed anywhere.
  3. Batteries are directly connected by wires for lighting.
  4. Engine A starts.
  5. Waiting 5-15 minutes.
  6. Engine A stops.
  7. Wires are removed.
  8. Engine B starts.

The advantage of this method is that almost nothing is done on the fly. And this is a serious claim for the safety of the procedure. The dead battery is recharged from generator A with normal voltage and good current. Disadvantages, in fact, only two. First, there is a possibility that a surge in voltage and current can harm the on-board network B. Second, the indicated time may not be enough for battery B to recharge enough to successfully spin the starter.

Method number 10. Superior 9th

An improvement is to disconnect battery B from its on-board network. Such an algorithm requires a couple of minutes more time to complete, however, it removes one of the two above-mentioned disadvantages. But the benefits, at the same time, remain. However, this method is not very suitable for those cases when, after removing the terminals from the battery, serious problems arise with car B. If you know about these, and they scare you, then it is better to use some other algorithm where you do not need to remove the terminals.

VIDEO: how to start a car with dead battery

Summing up

Surely many (perhaps even experienced) motorists did not even suspect that you can light a car in so many different ways. Meanwhile, these are not all possible options. Although only the nuances change further. Otherwise, all the basic and often used in practice algorithms for lighting a car are described here. If you have something to add on the topic - welcome to the comments below.