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Battery desulfation is often considered pure magic, which you either believe in or you don't. The reason for this attitude is simple. Almost everywhere where there is information about this method of car battery resuscitation, the chances of success are not mentioned. Many try and, having not received a positive result, go to the Internet, pregnant with negativity. Myths are born there, because of which distrust of this procedure naturally arises. But desulfation is a simple chemistry that, under certain conditions, really helps to save money.

Sulfation of battery plates

Batteries with specific plate sulfation
Batteries with specific plate sulfation

May the author of Auto without SRT be forgiven by candidates of chemical sciences, but there will be no formulas with complex terminology. The phenomenon of lead-acid battery sulfation can be easily explained in human terms. And you need this in order to understand how the reverse process works. I mean, the desulfation you came here for.

What is a battery? This is a plastic container divided into compartments (jars). Lead plates are placed in each such compartment. Also, regardless of technology, there is an electrolyte of water and acid. In order for the battery to work - to be charged and give off the accumulated energy, the electrolyte must come into contact with lead. The key point here is the contact area.

The following battery indicators depend on it:

  1. Rated capacity (A*h) - the larger the area of plates interacts with the electrolyte, the more energy the battery can accumulate.
  2. Maximum starting current (A) - it is the higher, the more lead is in contact with the acid.
  3. Voltage drop at load (V) - with an increase in the contact area, the battery holds the load more confidently.

Sulfation is the formation of lead sulfate on the plates during battery discharge. As a result, a light gray coating appears on them. If a discharged battery is immediately charged, this sulfate disappears. Then everything is repeated in a cycle throughout the life of the battery, and this is the norm.

Problems begin when the battery is idle for a long time in a discharged state. The sulfate formed on the plates hardens to such an extent that it can no longer dissolve during subsequent charging. Accordingly, if the jamb is repeated, a new one is added to the old plaque. As a result, we get a battery, the plates of which are closed from the electrolyte.

Lead sulfate under the microscope
Lead sulfate under the microscope

The area of contact between lead and acid decreases. As a result, the capacity disappears, the maximum starting current decreases, and the voltage drops under loads tend to zero volts.

Principles of battery desulfation

Battery desulfation is a process that is fundamentally opposite to the sulfation discussed above. When the battery is operated correctly - it is recharged in a timely manner - then this happens by itself, without any tricks and dancing with a tambourine. However, in real life, unfortunately, many car owners deprive the battery of their attention, as a result of which it rides under the hood in an undercharged state for most of its life.

The task that is solved by desulfation is extremely simple. It lies in the fact that it is necessary to somehow forcibly remove harmful sulfate, due to which the contact area of with the electrolyte decreases. Theoretically, this problem can be solved in several ways. In practice, not everything works. But for a deeper understanding of the topic, let's hook on all the main methods of desulfation.

One of the most obvious ways to remove sulfate from car battery lead plates is mechanical cleaning. Its principle is similar to cleaning metal from traces of corrosion. On the Web, you can find a lot of instructions that, in serious cabbage soup, describe this process in detail and clearly. Moreover, the authors of such materials undertake to guarantee that this method is very effective, and will definitely bring a battery that has died from sulfates back to life. In fact, mechanical desulfation is nonsense. If only because in order to gain access to the plates to clean them, you will have to savagely saw the case of a fundamentally non-separable battery.

Another desulfation method that bloggers do not hesitate to share for the sake of views and likes is purely chemical. It consists in the fact that it is necessary to fill a poor battery with some vigorous chemistry, which, due to its aggressiveness, is able to dissolve sulfate. What is not advised to pour - from banal soda to drugs like Trilon-B. Absolutely not a single adequate motorist, of course, would dare to use chemicals so harshly. And Auto without a service station also strongly advises you not to be so weird.

Do not pour any game into the battery - this is a utopia
Do not pour any game into the battery - this is a utopia

Of the adequate technologies for desulfation, only one method can be distinguished, for the implementation of which nothing needs to be sawed, drilled and poured into cans. It consists in the fact that sulfates are destroyed in the process of natural charging of the battery, but performed in a special way. How exactly this is done is described below.

Chances of Successful Desulfation

Often desulfation does not help
Often desulfation does not help

But first, it’s worth a little consideration of a question that for some reason is usually not paid attention at all. Meanwhile, it is always useful to ask this question before desulfating your battery. Perhaps the correct answer to it will help you save a lot of time, nerves, health and money. The bottom line is, will desulfating your battery help?

Assessing the chances of success of this procedure is quite simple. Desulfation is worth doing if:

  1. The battery is not "older" than 5 years (from the date of issue, not purchase).
  2. The electrolyte is transparent and does not have a brown tint.
  3. Your battery is a serviceable type and you have checked the electrolyte level at least twice a year.
  4. The battery has not stood idle in a discharged state for more than 3 months.
  5. There are definitely no shorted cans in the battery.

In all other cases, do not believe in any miracle methods and “special” memories, which are also discussed below. Nothing will help your battery. You are just wasting your time and money.

About memory with battery desulfation function

In our time of rapid development of electronics, you will not surprise anyone with a charger with a desulfation function. Although even now it is not difficult to find motorists who speak with skepticism about such devices. In fact, there are such memory devices, and they not only cost more than usual ones, but can really cope with sulfates on battery plates. But not always. As elsewhere, there are no miracles in this matter either, and the chances of a successful battery recovery depend not only on the charger.

Typical battery charger with desulfation function
Typical battery charger with desulfation function

Let us briefly consider how memory devices with a similar function really differ from conventional models.

Important clarification! The following are the differences, most of which are present only in those models that have the desulfation function not only in the form of an inscription on the case, but also in the filling. Unfortunately, the market is literally overflowing with chargers, on which the inscription “desulfation” flaunts, however, after opening it turns out that inside it is an ordinary dummy.

The first thing that distinguishes chargers with a desulfation function is a well-thought-out scheme for stabilizing and limiting charging characteristics - voltage and current. This is an extremely important condition for successful battery recovery, since the basis of the considered battery recovery technology is special settings and the exact dosage of the specified parameters.

The second difference is that the charger not only charges, but also “knows how” to discharge the battery. Moreover, right in the process of desulfation. There are many ways to implement such a function, starting with the simplest relays and ending with a program hardwired into a microprocessor.

Third, what is the difference between memory devices with a desulfation function - the charge is carried out by the so-called pulsating current. If you explain on your fingers, then this is a mode when the current is driven into the battery not constantly, but intermittently, in small doses. This avoids a quick recharge of the battery and achieves a better “knocking down” of sulfates.

The fourth difference, which not all models can boast of, is the presence of a function for estimating the real capacity of the battery. On the Auto without Service Station website, this is repeatedly mentioned in other materials about car batteries. The bottom line is that the capacity of a used battery is always less than indicated on the case. Accordingly, the charge current is also needed less. Otherwise, the battery will charge very quickly, but as if superficially. This means that high-quality desulfation is out of the question.

It is because of these differences that chargers with a desulfation function are noticeably more expensive than conventional ones. Often even more expensive than a new battery. Is it worth buying this? If you have only one or two batteries on the farm, then you will have to wait a very long time until such a memory pays off. In addition, with a great desire and knowledge of the theory outlined below, you can restore the battery with the simplest charger. Naturally, if your battery passes the five-point test above. If there are a lot of batteries that you need to service, or you do it for people for money, then buying a “smart” powerful charger is a must for you.

Battery desulfation with a simple charger

If, nevertheless, you decide to purchase a charger with a desulfation function, then you do not need to understand the essence of this procedure. The device corresponding to the declared description will do everything by itself. However, you can try to restore the battery using conventional charging. This is very possible, although it requires some knowledge and a lot of time. If you want to give it a try, here's a tried-and-true guide.

This is how the process of desulfation "on the machine" looks like
This is how the process of desulfation "on the machine" looks like

To begin with, it should be clarified which charger is suitable for desulfation, since not everyone will be able to do this. All you need is the ability to control and adjust the charging parameters. Namely, voltage and current. An ordinary multimeter is enough for control (two are better to monitor both voltage and current at the same time). But for adjustment, a voltage setting must be provided.

The desulfation algorithm is as follows:

  1. Determine the actual capacity of the battery. This can be done using a conventional car headlight lamp - charge the battery fully in normal mode, and then discharge the lamp until the voltage at the terminals drops to 10.5 V. The average current consumed by the lamp is calculated by dividing the power by the voltage. Further, knowing the current and time, calculate the capacitance (an example for clarity is below).
  2. Limit the charge current. The optimal current for both normal battery charging and desulfation is 10% of the capacity. Not higher.
  3. Limit stress. It should not exceed 14.4 V throughout the entire procedure. At the first stage, when the battery is completely discharged, the voltage at the above current will be in the region of 12.7-13.0 V. Further, as it charges, it will rise.
  4. Charge the battery. But not all the way, as in normal mode, but for 30-60 minutes.
  5. Discharge the battery a little. You can use the same bulb. Disconnect the battery from the charger, and load it with a lamp for 5-10 minutes.
  6. Repeat steps 4 and 5 until fully charged. That is, charge the battery, periodically discharging it. Continue until the battery is fully charged in this mode. The full charge can be judged by the current, which dropped to 0.1 A at a voltage of 14.4 V.
  7. Repeat if necessary. As a rule, if the battery is not heavily sulfated, one such cycle is enough to restore it. If the battery is badly killed, then it is advisable to repeat the procedure 2-3 times. But not more.

During manual desulfation, avoid:

  • battery overheating;
  • "boiling";
  • current above 10% capacity;
  • voltages above 14.4 V.
Battery load diagram with a lamp
Battery load diagram with a lamp

Upon completion of desulfation, for the sake of interest, you can re-measure the battery capacity. If it has increased, then you were not steaming in vain. After the next discharge, you can charge the battery in the usual mode, or go through the training cycle according to the above algorithm again.

Capacitance example. Let's say you have a battery with a capacity of 70 Ah declared on the case, and a 50 W headlight bulb. The average discharge voltage can be taken as 11 V, since it will gradually decrease from 12.7 V to 10.5 V. In this scenario, the average discharge current will be 50:11 = 4.5 A. Let's say that your battery was discharged by such a light bulb up to 10.5 V 12 hours. We multiply the current by the time, that is, 4.5 * 12, and we get the real approximate capacity - 54 A * h. Accordingly, such a battery should be both charged and trained with a current not exceeding 5.4 A (10% of the capacity).


Car battery desulfation is not magic, nor is it a myth. This is a very real recovery method that can be implemented in two ways. The first is to buy a special memory with the appropriate mode and trust the electronics. The second is to carry out the procedure in manual mode according to the algorithm described above. Of course, don't forget to evaluate your chances of success so you don't waste your time. Write in the comments below the article what you think about car battery desulfation, share your successes and failures about this.

VIDEO: battery desulfation (2 parts)