To charge a calcium battery correctly and up to 100%, a special approach is needed. Especially when it's off the car. With the standard approach, the battery can stand on charge for as long as you like, but it will never fully charge under such conditions. This will be seen by the density of the electrolyte, as well as by the indicator, which does not turn green. Although the tension of rest will indicate the opposite. How to charge a calcium battery up to 100% and not reduce its resource is described in detail with explanations in this article on the ABS website.

About voltage and density

These two parameters are important, as they allow you to assess the degree of charge of the battery with liquid electrolyte. And in this particular case, we need them in order to understand whether we have correctly charged the calcium battery. Therefore, let's start with how to navigate these parameters.


This refers to rest stress. It can be measured correctly only after the battery has stood without any work for at least 8-10 hours. During this time, all electrochemical processes in it will gradually stop. And voltage stabilizes. Very often they forget about this nuance, and measure it at random. As a result, the voltmeter shows inflated numbers, misleading the motorist.

If you measure the resting voltage correctly, then according to the obtained indicators, you can draw conclusions about the degree of charge of the battery. The same goes for a dead battery. Whatever state it is in, the rest voltage will “tell” how much percent it is charged. This can be determined using a simple table.

Quiescent voltage (V)

Charge (%)

< 11.90























Incorrect measurement


As real experience with calcium batteries shows, the transition to a state of rest often does not occur after 8-10 hours of inactivity. Sometimes you need to wait a little longer. For example, the author of this material regularly charges the calcium battery of his car with small currents for two to three days in a row. When the charge stops in the evening, then in the morning the voltage at the terminals is usually more than 13 volts. This means that the state of rest has not yet come.

Most likely, it does not occur for so long due to the fact that the day before there was a long charge with a small current. After all, when the battery is charged regularly from the generator, then in the morning the voltage is always adequate. That is, within the framework of what is listed in the table above. From this we can conclude: the longer the calcium battery was charged, and the lower the currents, the more it is necessary to wait for the onset of a state of rest.


This is a hydrometer - a device for measuring the density of the electrolyte in the battery
This is a hydrometer - a device for measuring the density of the electrolyte in the battery

We note right away that for owners of calcium batteries without traffic jams, this information is useless. If you have a serviced type battery, then you definitely need to know what electrolyte density is and how to determine the degree of battery charge from it. It is measured with an instrument called a hydrometer. You can also determine the percentage of charge according to the table. Although with some reservations related to the main feature of calcium batteries. But more on that later. For now, here's the board.

Density (g/cm3)

Charge (%)

< 1.12






















> 1.26

Density above normal


The advantage of density over resting voltage is that it does not take 8-10 hours to measure it. Correct readings can be taken at any time. Even while charging the calcium battery. But we repeat that with some reservations, which we will now begin to analyze.

Features of Ca/Ca battery

Calcium battery - structurally, it is a classic lead-acid battery, but with one difference. It lies in the fact that the plates in the battery are alloyed with calcium. That is, they are also made of lead, but covered with a microscopic plaster of calcium. This is done in order to prevent the process of electrolysis of the water contained in the electrolyte.

Electrolysis is one of the main problems of conventional batteries. It starts when the battery is more or less charged, and the charge voltage exceeds 14.5 V. During electrolysis, water decomposes into hydrogen and oxygen, leaving the battery forever. Visually, this process looks like boiling water in a kettle or saucepan, which is why, in fact, it got its name. Although electrolysis has nothing to do with the classical boiling of water, except for seething and bubbles.

In calcium batteries, this problem has been solved. And this had to be invented, because in the process of electrolysis, it is not just water that decomposes into its constituent components. It leaves the battery, resulting in a decrease in the electrolyte level. The electrolyte itself, at the same time, becomes more dense. The concentration of acid in it is growing, which is not good. Among other things, electrolysis adversely affects the condition of the lead plates of the battery. They gradually crumble, collapse, increasing the risk of a short circuit. In general, battery life is reduced. And thanks to calcium, it increases.

But this is not all that we currently need to know about calcium batteries. The fact is that the so-called boiling in classic batteries was to some extent a useful process. Thanks to him, the electrolyte in the banks was mixed, and its density was leveled. Calcium batteries cannot boil under normal conditions. In the process of charging, the denser electrolyte sinks lower, and the less dense remains on the surface. It is because of this that, with the classical approach to charging a calcium battery, the density measured by the hydrometer cannot reach the desired level in any way, and the indicator does not turn green.

In addition, recently there has been a lot of talk about electrolyte stratification. This is the process of its stratification. We will not consider chemistry. We only care about three things. Firstly, due to stratification, we will never be able to correctly measure the electrolyte density, since it will be underestimated in the upper layers. Secondly, an increased concentration of acid in the lower part of the battery adversely affects the lead plates.

Thirdly, if suddenly such a battery is discharged in winter to more than 30%, there is every chance that there will be clean water on top, and not electrolyte. It is clear that the battery will literally freeze. Sometimes it freezes so that the battery case cannot withstand the expansion of ice. Although this is not the only possible problem.

From the foregoing, it follows that charging a calcium battery in the traditional way is not effective. He won't die instantly, of course. But a potential five-year resource can easily be reduced to two or three years. Actually, these are all the features that you need to know about the Ca/Ca battery, if your goal is to charge it correctly and fully.

Official instruction

How do manufacturers recommend charging a calcium battery? They usually attach a brief instruction to it, in which, without any clear explanations, they write what to do. One of these official instructions is now on my desk, and we will take the key points from it.

The following is written in it:

  1. The calcium battery should be charged with a current equal to 10% of the capacity.
  2. When the charge voltage reaches 14.4 V, the current must be halved and charged for 10 hours.
  3. Upon completion of the charge, it is necessary to check the density of the electrolyte (hydrometer vs refractometer) and, in case of high concentration, correct it by adding water.
  4. Each time after adjusting the density, the battery must be charged at a voltage of 16 V, and carried out for 40 minutes.

This guide is really good. But it has several shortcomings at once. The author of this instruction did not say a word about those cases when the density at the end of the charge, on the contrary, is low. He also did not say anything about the fact that 16 V can adversely affect the car's electronics if it occurred to you to charge the battery without disconnecting it from the on-board network. In addition, there is nothing in this manual for those whose chargers can only be adjusted by voltage, or even automatic.

So, let's expand on this guide a bit. Rather, we will rewrite it from scratch, not forgetting about non-standard situations. We will also add to it a few recommendations that will extend the life of the calcium battery.

Calcium battery charging algorithm

If instructions for charging a calcium battery were instructed to write to me, then it would look like this:

  1. Estimate the state of charge of the battery by the rest voltage or the indicator on the case.
  2. If the rest voltage is below 12.3 V (or the indicator is not green), charge the battery using a charger.
  3. Disconnect the battery from the on-board network.
  4. If there are blockages, turn it out.
  5. Connect the charger, having previously set the charge current to 10% of the real capacity, and not from the one that is written on the case.
  6. Charge until the voltage reaches 14.4 V and the charge current drops to 0.1-0.3 A.
  7. If you are going to travel in the near future, then simply connect the battery to the car's on-board network.
  8. If you are not planning to travel, additionally charge the battery at 16.1 V for 40 minutes.
  9. If the density of the electrolyte up to the 8th point is normal, then it is not necessary to charge with a voltage of 16.1 V.
  10. The same is true if the indicator on the battery case turns green.

What has changed in the end compared to the official instructions? Firstly, we eliminated the risk of damaging the car's electronics with a voltage of 16.1 V. Secondly, we made it clear that the essence of the charge with a voltage of 16.1 V is to mix the electrolyte. If we are planning a trip, it will stir itself from vibration. If not, we forcibly provoke electrolysis with high voltage, that is, we boil the battery. Thirdly, we made it clear that a calcium battery discharged to 60% (and below) should be charged. Otherwise, sulfation will begin.

In addition, if you carefully read the proposed algorithm for charging a calcium battery, you can understand that it is suitable for almost all types of chargers. Even for do-it-yourselfers.

But that's not all. Even our supplemented instructions cannot be called complete. It does not have answers to many questions that are often asked by owners of calcium batteries. Therefore, let's spend a little more time and analyze 10 questions regarding this type of battery. By the way, many of the answers provided are generic. That is, they will also be useful in cases where the battery is not calcium, but some other - classic, AGM, GEL, and so on.

About car battery desulfation

Answers to frequently asked questions

The issues discussed below are not taken from the ceiling. Many of them were asked at one time by the author of this material, others were interested in friends and acquaintances. The answers to them are not so easy to find. Indeed, in "prominent places" on the Internet, one usually finds either scarce information or very different in meaning. That is, some "experts" say one thing, other "experts" contradict the first, and advance their ideas. The motorist can only guess - who speaks correctly and who is mistaken.

A few words should be said about where the answers to the questions presented below are taken from. Firstly, this is the author's personal experience - just the operation of Ca/Ca batteries, as well as experiments with charging them with different chargers and in different modes. Secondly, some knowledge was gleaned from specialized books, of which at least a dozen were read. Thirdly, it is logic and common sense l. As it turns out, this is important. After all, some "specialists" with You Tube shows this and talks about batteries, which is clear even without books with experience - this does not work.

What charger to charge a calcium battery?

Typical calcium battery charger
Typical calcium battery charger

If you need without dancing with tambourines, then a special charger for calcium batteries. These include those that have a 16.1 V charging mode. How to use such devices is clearly described in their operating instructions. The basic principle is based on what has already been said above.

You can charge a calcium battery with any other charger that has manual voltage adjustment. In this case, the whole process is divided into two stages. First, it is charged to a voltage at the terminals of 14.4 V and a minimum current. Then, for about half an hour, a voltage of 16.1 V is given. In this case, the current should also be taken into account, since it can be very large if the specified voltage is immediately set.

If the charger is not special, and it does not provide for voltage adjustment, it will not work to charge a calcium battery stationary up to 100%. However, as real experiments show, this can be achieved by mechanical mixing of the electrolyte instead of boiling with increased voltage. All that is needed for this is to install the battery on the car and drive a few kilometers on not the most flat road. After that, as a rule, the density evens out and the indicator on the case turns green.

What voltage to charge a calcium battery?

For a full charge, a voltage of at least 14.4 V is required. If the battery is charged stationary, then at the end it is necessary to forcefully mix the electrolyte by electrolysis. You already know how much tension to provoke him. Under the hood, under normal conditions, there is no such problem, since everything is perfectly mixed from vibrations. It is very useful to turn to logic and common sense here. If manufacturers know that the voltage of the on-board network on cars is 14.4-14.8 V, then they would make batteries that cannot do without 16 V.

On the Internet, there are smart people who put forward the bad idea that calcium batteries should not be bought for a car at all. Like, there is no voltage sufficient for a 100 percent charge under the hood, which means that the battery will quickly die from sulfation. This is nonsense caused by misunderstanding. Real experience confirms this. If there are no generator malfunctions in your car, the calcium battery will serve the prescribed 5 years without any problems. And even longer.

The author's personal record is 11 years (together with the previous owner of the car). This is how long the calcium battery lasted on the car, according to the release date stamped on the case. True, for the last year and a half, the capacity in it was on the strength of 15 ampere-hours, and it often had to be supported by a charger. She died due to the fact that there was a short circuit in one of the cells.

How much current to charge a calcium battery?

Probably everyone knows that the charging current should be no more than 10% of the battery capacity. This is the golden rule. But it's a trick. The fact is that the capacity of the batteries is constantly decreasing during operation. And most motorists continue to charge them 10% of what is written on the case. This leads to the fact that the battery is not fully charged, and its service life is ultimately greatly reduced.

What is the difference between the real capacity and the one written on the case?

Chinese battery capacity measuring device
Chinese battery capacity measuring device

Therefore, you need to understand what kind of capacity to take 10%. While the calcium battery is new, there is every chance that it has as many ampere-hours as it is written on the case. But a year later, this figure is noticeably reduced. Even if you take care of the battery, avoiding modes that are harmful to it. The actual capacitance can be measured with special devices. If there is no desire to buy them, then simply after each year of battery service, discard 10-15 ampere-hours from the original capacity on the case. Already from this figure, take 10%, and charge.

How long does it take to charge a calcium battery?

Charging time for a calcium battery depends on the following factors:

The larger the capacity and the degree of discharge, and the lower the current, the longer it will take to charge. On average, a fully discharged 60 ampere-hour calcium battery with an initial current of 6 A is charged in 15-20 hours. Not 10 because the battery "assimilates" not all of its given energy. Over time, this time decreases, as the battery loses capacity, and it is often continued to charge it with the same six amperes. In the last stages of life, the battery can be charged in just a couple of hours.

How to charge a maintenance-free calcium battery?

The only difference in this case is that it is not possible to directly measure the density of the electrolyte. Accordingly, one of the methods for assessing the degree of battery charge disappears. It remains to be guided only by the indicator on the case, as well as by the rest voltage. In all other respects, the algorithm is the same as for serviced calcium batteries. Learn more about charging maintenance-free batteries.

Is it necessary to charge with 16V?

No, not necessarily. If a calcium battery by all indications “feels” normal under the hood of a car, there is nowhere for 16 volts to come from. As for stationary charging, then in these cases it is not at all necessary to “boil” the electrolyte with increased voltage. It will be mixed from vibration right on the car.

If the calcium battery is in storage, or in some kind of fixed system (for example, it accumulates energy from solar panels or a wind generator), then 16 V cannot be dispensed with. Otherwise, the battery is waiting for the sulfation of the plates and the stratification of the electrolyte.

Is it possible to charge a calcium battery directly on the car?

Here it means whether to remove the terminals. The fact is that on many modern cars (and not very modern ones), disconnecting the battery from the on-board network leads to certain problems. In particular, certain settings can be reset, idle speed can float, and so on. So. If disconnecting the battery causes you this kind of problem, then you can charge without removing the terminals.

However, it is not worth giving a voltage of 16.1 V with the on-board network connected. Often because of this, unprotected electronics burned out. In particular, freelance budget gadgets often suffer from such exploitation - radio tape recorders, recorders, alarms, navigators, and so on. In such cases, it is better to hope that the electrolyte will mix in the process of movement.

Why is the charge indicator not turning green?

Calcium battery status indicator
Calcium battery status indicator

If you carefully read what is written above, then you already know the answer to this question. If a calcium battery is charged without “boiling” at the end, then the density of the electrolyte in the upper layers will be reduced. And the indicator is a kind of float that works in the upper layers of the electrolyte. As a result, if the battery is not "boiled", the ball does not pop up, and the window does not turn green. As practice shows, after a short trip on rough roads, the indicator of a battery charged without boiling turns green.

Do I need to charge a new calcium battery?

On the topic - whether it is necessary to charge a new battery - a separate article has been written. The information presented in it applies to all types of batteries, including Ca/Ca. Come on. Read.

Brief summary

As can be seen from the above, charging a calcium battery has its own characteristics. And all due to the fact that this type of battery has protection against boiling. Under the hood, this is a useful thing. But when charging from a stationary charger - a difficulty that has to be overcome with increased voltage. In general, as experience shows, if you charge a calcium battery regularly, in a timely manner and correctly, take care of it and follow it, then it lasts a long time. More than 5 years. Checked.

A master class with a photo report on recharging a calcium battery before winter was released on the ABS website.

VIDEO: charging calcium battery