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To choose a charger for a car battery, most motorists are guided only by price tags. This is fundamentally the wrong approach. Moreover, good in this case is not necessarily expensive at all. When choosing a car charger, you need to consider how and what you plan to charge with it. Otherwise, you risk buying air at the price of nanotechnology.

10 criteria for choosing a charger

Despite the apparent simplicity, a normal charger has at least a dozen parameters. Yes. Not all of them are critical. But only until you think about them. The purpose of this material is to tell in simple words about all the main features of the charger for the battery, which you should look at before buying in the first place.

The choice of charger will be made based on the following 10 criteria:

  1. Charging voltage.
  2. Max charging current.
  3. Real power.
  4. Choice of charger by battery capacity.
  5. Availability of indication.
  6. Manual adjustments.
  7. Special charge modes.
  8. Charger technology.
  9. The presence of protection.
  10. The quality of the clamps and power wires.

Unfortunately, some of these points cannot be applied if the charger is selected online. However, let's not forget about our consumer right to return the purchased product within 14 days if we are not satisfied with it. If you choose in a live store, where you can feel and carefully examine the device, then there are no problems.

By the way, catch useful advice about this. If you really want to choose a charger in any online store, do not rush to pay for it. Add to cart. Then, if there is a good car shop nearby, visit it and try to find a model you like. It will most likely cost more. But on the other hand, you can hold it in your hands and evaluate what cannot be done from a picture on the Internet. Real experience shows that sometimes, after examining the charger "live", there is no desire to buy it at all.

Charging voltage

Here, at first glance, everything is outrageously simple. If we choose a car charger for a passenger car, the nominal voltage should be 12 V. Accordingly, the main task is supposedly not to buy a 6- or 24-volt one. But life is not so simple. The fact is that a standard battery is charged with a voltage not of 12 V, but from 12 V to 14.4 V.

The pattern is simple. The deeper the battery is discharged, the more current it can draw. We (or memory) are obliged to limit this parameter. Therefore, in the first stages of charging, the voltage should be maintained in the region of 13.1-13.5 V. As the battery charges, the indicators increase. The increase in voltage continues until it reaches the maximum allowable. Usually it is 14.4 V. After that, it must be held without letting it rise. Otherwise, the battery will start to “boil” with all the ensuing consequences.

Charging voltage
Charging voltage

How to use this information when choosing a charger? If you are aiming for an automatic model, it will most likely "take care" of the correct voltage at the battery terminals during charging. But not always. Some memory devices, although they are positioned as automatic, cope with this task very badly. Especially often they sin with the maximum charging voltage, which strives to “boil” your battery. Checking this item is easy if you buy in a live store.

Models with manual adjustments, which are discussed a little below, are less insidious in this regard. In which case, you yourself can adjust the charge voltage. As for the choice of a charger without automation and adjustments, everything here is sad and unpredictable. They can turn up the voltage up to 16 V and above. There are also those that “fry” up to 19 V. It is clear that the battery will die very quickly with such operation.

An important point about tension. If the selected charger has a voltmeter, do not be too lazy to check its readings. It often happens that they lie. It's easy to check. Connect a tested multimeter directly to the battery terminals in voltage measurement mode, and compare its readings with the numbers on the charger screen. Don't let the phrase "tested multimeter" scare you. Almost all of them have sufficient accuracy. Even the cheapest ones. If they lie, then by hundredths of a volt, while voltmeters on chargers sometimes go aside by half a volt.

Max charging current

The characteristic is selected according to the capacity of the battery that is planned to be charged. But this is discussed separately. Here I would like to focus on such a concept as limiting the charging current. The ability to somehow limit the current strength must be present. An exception can only be low-power chargers, which, due to their wretchedness, are fundamentally unable to deliver currents of more than 2-3 A.


With current limiting, everything is the same as with voltage. If you choose an automatic type charger, it should take care of itself. Moreover, on many models there are presets that allow you to manually set the maximum charging current. Options with manual adjustments are also good in this regard, since you limit the current with the handle at the very beginning, and in the further charging process it will only decrease. Needless to say, that with the choice of a charger without automation and any adjustments, everything is sad?

Why is charging current so important? There are several reasons. Firstly, it is impossible to regularly charge the battery with too much current. This reduces its overall resource. Secondly, the lower the charge current, the better the battery is charged. That is, if you are not in a hurry, charge the battery of your car with as little current as possible. Yes. It's longer. But on the other hand, the battery during such operation is better charged, and its overall resource is also significantly increased.

By the way, this rule also works with batteries in your phones, tablets and other gadgets. Therefore, if you want your smartphone to charge more “densely”, charge it not from a regular charger that produces a current of 1-2 A, but from a USB port on a computer or laptop. There is only 500 mA (half of 1 amp), which, of course, will extend the charge time. But on the other hand, the battery charges better, does not heat up, holds a charge longer, and lasts for many years. Checked.

Real power

Few people look at the declared power when choosing a charger, since this characteristic seems unimportant. However, sometimes it helps to understand if other numbers in the description of the model are exaggerated. Unfortunately, this kind of thing happens all the time today. Therefore, always pay attention to power.

If someone forgot from school, then power is voltage multiplied by current. How to use this when choosing a charger for a car? Elementary. Let's say the characteristics of the model you like indicate that the charger delivers current up to 10 A and has a power of 100 watts. As you already know, a car battery charges up to 14.4 V. That is, in order to give out the declared 10 A for which you will pay your money, it must have a power of 144 W (10 A × 14.4 V). We already see that somewhere we are being deceived.

But that's not all. The fact is that we calculated the power that should be at the output of the selected charger. And in the characteristics, the manufacturer or seller is obliged to indicate the watts consumed from the network. No matter how high-tech the memory is, its efficiency is far from 100%. This means that part of the energy is spent on heating, the operation of auxiliary elements, and so on. That is, in fact, the charger discussed above should have a real power of at least 200 watts. If not 250 watts.

By themselves, watts are not very important to us, as motorists. But this kind of cheating means that the maximum charging current of the chosen charger will be much lower than what we will pay for. Don't be lazy. Check these figures on the proposed models. You will be surprised how many positions suffer from this particular sin.

Choosing a charger by battery capacity

This point is closely related to the maximum charge current and to the power discussed above. The choice of a charger by battery capacity is carried out as follows: the capacity indicated in ampere-hours is taken and divided by 10. The resulting figure is the maximum allowable charge current for your battery. That is, the selected memory should provide you with such a current. It is better with a margin so that the device does not work at the limit of its capabilities. Will last longer.

An example for clarity. Your car uses a battery with a capacity of 70 Ah. This means that at the first stage it can be charged with a current of 7 A. Accordingly, you need to choose a charger that is capable of delivering such a current. If you take it with a margin, then we throw in a couple more amperes. As a result, look for a model that is capable of delivering 10 A.

Regarding the charging current and battery capacity, one point should be clarified. It consists in the fact that only new batteries have the capacity declared on the case. During operation, literally every day, this parameter decreases. It follows from this that a non-new battery with a declared capacity of 60 A*h should not be charged with a current of 6 A. If such a battery is a couple of years old, then it remains (depending on how it was used) from 30-40 A*h. And even less. Consider this not only when choosing a charger, but also when charging batteries of different age.

Availability of indication

The presence of indication is an important criterion, which should not be neglected. It is needed in order to control what the selected charger does with your battery. Of course, you can measure volts and amps with a multimeter. But it's inconvenient. In addition, the multimeter cannot replace some types of indication.

Charger without indication
Charger without indication

The first thing a good car battery charger should have is an ammeter and a voltmeter. The first device is on almost all models. Although their accuracy and information content often leaves much to be desired. As for voltmeters, for some reason they are considered not very important devices. But in vain. The resource of the serviced battery largely depends on the charge voltage, therefore it will not be superfluous to periodically monitor it. Even if the memory is fully automatic.

Charger with voltmeter and ammeter
Charger with voltmeter and ammeter

Having chosen a charger with a voltmeter and an ammeter, do not be too lazy to check their accuracy. This can be done with a simple multimeter. To check the readings of a standard voltmeter, turn on the multimeter in the DC voltage measurement mode in the range up to 20 V, and connect the probes directly to the battery terminals. The ammeter is checked with the same multimeter. Only now it is necessary to turn on the appropriate mode on it, rearrange the probe into the appropriate socket, and add it to the circuit in series (between one of the battery terminals and the memory clamp removed from it).

It is important that you need to control the voltage exactly at the battery terminals. As a rule, if the standard voltmeter on the memory is not calibrated, it shows what is at the output of its circuit. And between this point and the battery terminals there are more wires. Often not the best quality. Accordingly, the voltage at the terminals may not be the same as that shown by the device on the charger. With amperes, this problem is absent, since the current strength in the circuit is the same everywhere.

The second type of indication is LEDs or bulbs (in older models), as well as icons on the display of cool chargers. Very useful, because if available, they allow you to control:

  • the presence of mains voltage;
  • is the battery being charged?
  • end of charge;
  • correct connection of crocodiles;
  • overload;
  • short circuits;
  • overheating and other parameters.
Charger with LED indication
Charger with LED indication

We repeat that the presence of such indicators is by no means obligatory. But if it is possible to choose a charger with them, it will only be a plus. At the same time, it is better not to buy a memory without a voltmeter and ammeter. You are tormented either to control the voltage and current with a multimeter, or to frequently change damaged batteries. And this is not an exaggeration.

Unfortunately, the presence of indication still significantly increases the cost of chargers. Although their implementation at cost costs the manufacturer mere pennies. This applies to both the indicators themselves and the schemes that control their work. But this is so, for the general development.

Manual adjustments

This includes either smooth voltage and current adjustments, or software presets in automatic chargers. On the one hand, it may seem that not everyone needs such difficulties. Many people prefer to buy appliances in the style of "plugged in and that's it." However, buying a charger without any possibility to adjust its operation is not worth it.

Charger with manual adjustments
Charger with manual adjustments

There are several reasons for this. Firstly, today you do not want to regulate anything, and tomorrow you decide to charge the battery consciously and correctly. If there are no adjustments, then you will not be able to do this. Secondly, over time, any electronics wears out. The charging characteristics issued by it will inevitably change. For example, the maximum voltage will decrease or increase, which will cause your battery to either not fully charge, or constantly “boil”. The presence of adjustments and knowledge of the elementary rules for charging the battery will allow you to quickly solve this problem.

Special charge modes

This point is considered here purely for the sake of informative material. That is, it will be useful for you to know that such modes exist, but it is up to you to overpay for their presence or not. Practice shows that there is little sense from them. Some of them even adversely affect the battery life. And those that were invented on the basis of myths about battery charging deserve special attention and caution.

There are special modes such as:

  • Desulfation - in theory, allows you to remove sulfates on lead plates, thereby returning some of the lost capacity. In practice, it doesn't always help. Especially if the sulfation of the battery is significant.
  • Training is the same as desulphation.
  • "Swing" - a mode in which at the last stage of charging the device periodically stops and then resumes the process. In theory, it allows you to more efficiently and fully charge the battery. In practice, the usefulness of this mode has not been proven by anyone.
  • Standby charging - allows you to keep the battery in a charged state for a long time not used. In fact, the mode is useful for those who have a quickly discharged battery, have generator malfunctions or high leakage current. In other cases, this is a useless addition.
  • Fast charging is a mode that allows you to revive a completely discharged battery in the shortest possible time. This is done due to the large charging current. It is harmful to the battery, so you should not use this mode often if available.
  • Quick start of the engine is an even tougher mode that allows you to make the starter rotate immediately after connection.

There are other modes, but they are either useless or designed to increase charger sales. If you want something from the above, then the most harmless and sometimes useful is desulfation or training. But remember that it only helps when sulfation is at an early stage. If the plates have been “overgrown” with sulfates for a couple of years, and you just now paid attention to this, desulfation will no longer help.

By the way, simulating such modes as desulfation, training, standby charging and “swing” is perhaps the most primitive charger. The main thing is to understand why this or that mode is needed, and on what principle it works. Unfortunately, it is not possible to describe all this here, since these are topics that require separate articles.

Charger manufacturing technology

Today you can choose one of two types of charger:

Transformer chargers - have a simpler device and are usually cheaper than pulse chargers. Among the shortcomings, the most significant is the relatively large weight and dimensions. Very often they are sold in large, solid-looking cases, while after disassembly it turns out that you bought air at the price of nanotechnology. However, transformer (they are also linear), as a rule, are reliable, because they have a simple device. There are also advanced models stuffed with electronics. But they are standing mother do not worry.

Transformer chargers
Transformer chargers

Pulse chargers are more compact, lighter and more expensive. Often they have good indicators for stabilizing voltage and current, as well as informative screens and additional functions. When choosing, you need to pay attention to the declared characteristics discussed above. Very often they are unscrupulously inflated. Although, in itself, the circuitry of switching power supplies implies high power with small sizes.

Pulse chargers
Pulse chargers

Availability of protections

With protections, the logic of manufacturers is similar to the indication. If they are, then you definitely need to raise the price of the model. Although the implementation of any of them costs a penny in practice. However, choosing a charger without protection is not worth it. Even if you are an experienced car enthusiast. Any user can make a sad mistake. Moreover, most often the chargers are used in the morning, when the sleep has not really passed yet, and the dead battery spoiled the mood, and the rush.

Protection can be from:

  • power surges;
  • polarity reversal;
  • overload;
  • overheating;
  • recharge;
  • power off and then on again.

For clarity, let's briefly consider the last point. Imagine that you put the battery on charge, selecting or manually setting the desired mode, and went about your business. And in the process, the electricity went out. The charger turned off, the settings were reset. Then the electricity turns on, but you still haven’t approached the battery. A charger without protection in such a case begins to charge the battery, as if it had been reconnected. That is, a large current and it is not clear what voltage. If there is protection, in the event of a power outage, the charger will “remember” the settings and the achieved charge mode, and after restarting it will competently resume the process.

Charger with protections
Charger with protections

It is clear that inexpensive chargers will most likely not have the described protection. It's not so scary. But as for the protection of polarity reversal and short circuits, it’s better not to buy without them. Practice shows that even the most experienced and attentive motorists can accidentally touch the plus to the "mass" or even mix up the polarity in the morning twilight.

Quality of clips and power wires

This is the last on our list, but not least, what you should pay attention to when choosing a car battery charger. Unfortunately, even very expensive and branded models are often equipped with too thin wires and worthless crocodiles. All this then quickly breaks down, heats up, melts and even catches fire. Therefore, pay attention to which wires the Chinese have attached to the charger you choose. Especially if it comes with the declared high currents.

In extreme cases, you can put your own wires and crocodiles. It often happens that the charger itself is not bad on the web. Do not buy it, perhaps, only because of the manufacturer's profitability? You can pick up high-quality power wires on your own, or buy a ready-made set that is really designed for high currents. Well, solder them - either yourself, or contact a friend who knows how to hold a soldering iron in his hands.

Which charger to choose in the end

Rule one: if you don’t want to shorten battery life, immediately abandon the cheapest models. There is definitely nothing of value among them. And some are even dangerous. Rule two: strive to choose a car battery charger with an indication. At least with an ammeter and a voltmeter. Rule three: Refuse to buy a model without foolproofing. Fourth rule: do not forget to choose the memory for your battery by capacity and type. Rule five: do not buy an inadequately expensive professional model for personal occasional use. Most likely, most of the features embedded in it will never be useful to you.

VIDEO: about choosing a charger for a car battery