In one of the previous materials about charging car batteries, we already wrote that a certain advantage of serviced batteries is the ability to control the condition and level of electrolyte, which allows you to extend the battery life and even revive it after a long period of inactivity without a charge. This issue is worth considering in more detail - although more and more car owners are choosing maintenance-free batteries, the demand for batteries of classical design remains. Checking the electrical parameters of the battery is relevant for all types.
What is the point of diagnosis?
The main parameters that are important for the owner are how the battery behaves under real load (voltage dips, maximum current) and its actual capacity. Even a fully charged battery (measured by a voltmeter or roughly by the built-in “eye”) does not guarantee a reliable start - if there are significant deviations in the level and density of the electrolyte, or “scattered” plates, it will be unable to maintain normal starter speeds and slowly gain a charge. Diagnostics will help to determine exactly what the cause of the problems is - in the battery, poor contact of the ground wire or in the starter itself.
Already relying on knowledge about the incorrect operation of the battery, you can (if it is, of course, serviceable) find out whether the malfunction is fixable - after spending some time, you may be able to save a significant amount. There is a special sense in checking the electrolyte density in winter - for example, a fully charged (that is, having a normal electrolyte density) battery will freeze at a temperature of about -54 degrees, and if the density decreases by only 0.15 g/cm 3 - already at -8.
Video: How to do battery maintenance
How to check electrolyte level
The composition and quality of the electrolyte largely determine both the efficiency of the battery and its service life. The electrolyte itself is dilute sulfuric acid, which participates in chemical reactions on the surface of the plates: during discharge it is consumed (lead sulfate is formed), and during charging it is restored.
For the correct course of the reaction and achieving the required resource, the density of a fully charged battery is normalized at 1.27-1.28 g/cm 3 for a temperate climate; for colder climates, it is customary to increase the density, thereby compensating for the slowdown in the progress of chemical reactions in the cold (up to 1. 31 g/cm 3).
When the battery is operating, the electrolyte level inevitably drops: the inevitable electrolysis of water, which occurs at , reduces the level and increases the density. With a long-term discharge, part of the acid remains consumed in the form of large crystals of lead sulfate, which will not be restored during subsequent charging - the density will drop.
Video: How to check the electrolyte level in a battery
The level of electrolyte in each jar is no less important - the electrolyte must cover the plates with a reserve in order to fully use their useful area even during fluctuations (rolls, sudden acceleration or braking). The easiest way to check it is that batteries with translucent walls usually even have marks on them, by which you can see the minimum and maximum levels. In opaque batteries, you can use any transparent tube by unscrewing the cap and releasing the tube into the hole until it touches the plates: by holding the top edge of the tube with your finger and pulling it out, you can see how much the electrolyte is above the plates. Normally, this excess should be 10-15 millimeters.
Was the level lower? Well, it's worth making up for. In theory, it is enough to add distilled water, since it is consumed first. But in practice, especially if the battery has already worked for a long time, such topping up can lead to a drop in density - as we wrote above, part of the acid will be consumed by undissolved lead sulfate. Therefore, you need to make sure exactly what the density of the electrolyte is at the current moment.
How to find out the density of the electrolyte?
To control the density of the electrolyte, a simple device is used - a hydrometer. This is a transparent tube with a bulb for collecting electrolyte, in which an indicator weight of a predetermined density floats. Opposite this weight there is a graduated scale - accordingly, depending on the ratio of the densities of the weight and the electrolyte being tested, it will indicate different scale divisions, which is what we need. The built-in “eyes” work in approximately the same way, but much more crudely - a green ball floating in a dense electrolyte becomes visible in the light guide of the indicator, but if it sinks (the density has dropped) - there is blackness in the eye.
Hydrometer device
Since the density of the electrolyte significantly depends on its temperature, it is best to measure it on a warm battery. If this is not possible, the following amendments are accepted:
| Temperature | Density Correction |
| -55…-41 | -0,05 |
| -40…-26 | -0,04 |
| -25…-11 | -0,03 |
| -10…4 | -0,02 |
| 5…19 | -0,01 |
| 20…30 | 0 |
| 31…45 | +0,01 |
Density measurements begin when the battery is fully charged. The nose of the hydrometer is lowered into the jar, then the electrolyte is taken into it with a pear. The pointer determines the current density. If the level is within normal limits, then the density should be normal.
Video: How to check electrolyte density
If the electrolyte level decreases significantly, the composition of the top-up is determined by the density: if it is higher than normal, then distilled water is added, but if it is lower, then acid will have to be added. However, how to determine the required amount without knowing how much electrolyte is left in the jar? The most optimal and reliable method is to completely drain the electrolyte from the jar and replace it with a ready-made one with a standardized density.
It is safest to pour the electrolyte into a wide plastic basin filled with several liters of water - in this case, water will splash, not acid, and the final concentration of acid will be low enough for safe disposal. Draining the electrolyte will allow you to simultaneously check for the presence of sediment in the jar: it will clearly indicate destruction of the plates. If you find sediment in one of the jars, you need to drain the electrolyte from all of them, then rinse all the jars, filling them two or three times with distilled water, and only then fill them with fresh electrolyte.
Battery charge level monitoring
Density monitoring is convenient because it allows you to assess the condition of each battery bank. But not everyone has a hydrometer, and this method is not applicable to maintenance-free batteries. Knowing the characteristics of a lead-acid battery, you can roughly estimate its charge using a voltmeter - without load, its readings should be in the range of 12.8-13.2 V, since a 12-volt battery has 6 series-connected banks, and when fully charged, each has a voltage on the terminals at 2.2-2.4 V. The battery is considered discharged if the voltage on the bank drops below 2.03 V (that is, 12.18 V in total).
Video: Checking the battery charge with a load fork
The roughness of this method of assessment lies in the fact that the voltage on all banks is summed up, regardless of their condition. For example, if five out of six jars are fully operational and charged, and a short circuit occurs in the sixth, then on the voltmeter we will see 10.75V - it would seem that the battery is in a deep discharge, but attempts to charge it will only lead to “boiling off” of the electrolyte in the serviceable jars .
But even if the voltage at the terminals is normal, it is not a fact that the battery will be capable of delivering the required current. To monitor current output, load devices are used - in the simplest case, this is a conventional load plug, consisting of a powerful low-resistance resistor and a voltmeter; the most complex devices (used, in particular, in dealer auto repair centers) have built-in electronic circuits, based on the voltage drop across a less powerful load. from the pre-entered nominal capacity, determining the condition of the battery. Since the price of such devices makes their purchase unjustified for the average motorist (in particular, the Micro 568 battery tester costs about 16 thousand rubles), we will focus on load forks of a traditional design.
By connecting the plug terminals to the battery, you can see the voltage on it - based on the above values, you can roughly determine its state of charge; many devices have color codes (green/yellow/red range) for convenience. By pressing a toggle switch or button on the case, we connect to the battery a load whose resistance is tenths of an ohm - thereby simulating the activation of a starter with a power of about a kilowatt. At this moment, the voltage at the terminals will drop sharply and begin to decrease even more. A battery can be considered serviceable if turning on the load does not cause a voltage drop of more than 2 volts (for commonly used 55-65 A*h batteries, the larger the capacity, the smaller the drop should be), and further reduction in voltage occurs slowly and smoothly. A sharp drop in voltage is a clear indication that the battery is no longer able to deliver high current, and its rapid decrease within a few seconds means a significant drop in battery capacity.
It is believed that modern batteries do not require special monitoring and fully perform their functions without any maintenance. This is partly true - if operation occurs under normal conditions, nothing needs to be done. However, with extreme driving and frequent charging/discharging cycles, the amount of liquid in the compartments gradually decreases, which leads to a decrease in battery capacity. In this article we will tell you how to check the electrolyte level in a battery without the help of a mechanic.
Conventionally, batteries can be divided into two types: serviced and maintenance-free. In the latter case, the design does not provide access to the compartments and manufacturers do not recommend opening the case yourself. Otherwise, you will break the seal, and you will hardly be able to seal the plastic case properly. Such manipulation will lead to the fact that the battery will have to be thrown away. In a maintenance-free battery, the amount of electrolytic mixture can be determined in two ways.
By control marks
On the body of such batteries there are “min” and “max” marks placed on an oval eye made of transparent material. The electrolyte level should be between these marks. If it is lower, it means that some of the distilled water has evaporated or flowed out through the safety valves. This usually happens due to improper charging or after the service life has expired.
If there is no peephole, carefully inspect the surface of the case. It is usually made of transparent plastic, and has a scale on one side. The marks will be the same as on the transparent eye.
By indicators
Modern models of imported and domestic batteries can be equipped with indicators. People call them “magic eyes”. The indicator changes color depending on the amount of charge and the density of the electrolytic mixture. To check the solution level in your car battery, follow these steps:
- using a clean rag, thoroughly wipe away the dirt and dust near the indicator;
- lightly tap the indicator with your finger - this will remove oxygen bubbles and you will be able to see it better;
- look at the color that appears on the indicator.
Green indicates that the level is normal, the charge is maximum. White – you need to connect the charger. Red – increased acidity of the solution, that is, the amount of water has decreased.
This control method is the most inaccurate; it can only be used if the battery is maintenance-free and other diagnostic methods are not available.
Inspect the battery housing.
Methods for checking the level in a serviced power source
The serviced battery is designed so that the owner can perform all the work independently. You can determine the fluid level in battery cans of this type with greater accuracy and, if necessary, add distilled water. There are two methods that allow you to control the amount of electrolytic mixture in the compartments. Let's look at each of them.
Using a measuring tube
You can check how much electrolyte is left in the battery using a simple device, which is a transparent tube whose diameter is smaller than the diameter of the plug. In exceptional cases, you can use part of a transparent ballpoint pen by first unscrewing the caps from it. The measurement is performed in the following sequence:
- remove dirt and dust from around the plugs;
- place the battery on a flat surface;
- carefully lower the tube into the compartment without tilting it;
- pinch the top hole with your finger;
- remove the tube without removing your finger, measure the amount of liquid in it.
Normally, the solution should cover the electrodes by 1 - 1.5 cm. If you have that much liquid in the tube, there is nothing to worry about. If it’s more, it means that last time you filled in more than you needed, pump out the excess.
You can clearly see how much electrolyte is in the jars.
Visual definition
This method can be used if the housing design provides special recesses at the bottom of the neck. The upper layer of liquid, touching the recesses, bends, forming the so-called “meniscus” or “eye”. By its location you can understand what the electrolyte level is at the moment. The “eye” is clearly visible - the level is normal; if it is not visible, the amount of solution has decreased.
Car enthusiasts often ask what the acid level in the battery should be. The wording of this question is incorrect. An electrolyte consisting of distilled water and acid is poured into the jars. Therefore, the methods described above make it possible to determine how much of the electrolytic mixture remains, and not its components.
The amount of electrolyte in batteries of different capacities
In some cases, it is necessary to completely replace the solution. Trying to find out how much liquid is required based on the level in the jars will not give any result. Unfortunately, manufacturers do not indicate the volume of the compartments, so you have to calculate it based on the battery capacity.
For these cases, we have prepared a table of correspondence between the amount of solution and the parameters declared by the manufacturer; you just need to find these values on the stickers or in the instructions.
|
Battery type |
Nominal capacity (Ah) |
Electrolyte quantity (liters) |
The indicators given in the table are relevant for domestic batteries. The maximum permissible error in the electrolyte volume should not exceed +/- 100 g. If you have an imported power source, then rely on its capacity indicated on the case or in the manufacturer's instructions. In difficult cases, it is better to get additional advice from the seller or an auto electrician.
Now you know how to check the electrolyte level in the battery. We recommend performing this procedure at least once a month in order to notice the problem in time and take measures to eliminate it.
A modern car must have a battery as part of its system. She is responsible for starting the engine, as well as all the electrics of the car. When performing maintenance, you should remove dirt from the battery and check its charge level.
You can carry out the measurement procedure yourself. To do this, first of all, you should find out what level of electrolyte should be in the battery. Experienced auto mechanics are ready to give a number of recommendations for servicing your car battery.
Device Features
Before you find out what electrolyte level should be in the battery, you need to study its structure in more detail. There are two types of batteries. They are divided into maintenance-free and maintenance-free batteries. Recently, the second type of device has become more popular.
Serviced batteries have the ability to add electrolyte inside if necessary. However, this will require certain tools. Maintenance-free batteries are replaced with a new device after their service life is exhausted. When such a battery is unusable, the indicator will glow dim green. In this case, the battery life cannot be extended.
The electrolyte creates a certain environment that accumulates electricity through a chemical reaction. This solution is concentrated sulfuric acid in distilled water. When these two substances interact, a large amount of heat is released.
Electrolyte density
When considering what the electrolyte level should be, it is necessary to talk about its permissible density. Sulfuric acid in its pure form is characterized by a fairly high value of this indicator. Its density is 1.8 g/cm³. 
The electrolyte in the battery should not exceed the level of 1.44 g/cm³. Density can vary from 1.07 to 1.3 g/cm³. The temperature of the mixture will be about +15 °C. The quality of sulfuric acid must be high. Otherwise, the battery may quickly become unusable.
Low electrolyte levels cause the internal plates of the device to dry out. In this case, it will be impossible to restore the battery. Therefore, it is important to know how to recharge the battery.
Why does the level change?
The electrolyte level in a car battery may change due to natural reasons. It is considered normal if the amount of liquid in the battery capacity is above its plates at the border of 11-15 mm.
The amount of electrolyte is assessed visually. Its decrease occurs due to the evaporation of water from the solution. This increases the concentration of sulfuric acid. The density of the solution will be higher than the original value. 
If all unfavorable factors are combined simultaneously during the operation of the machine, the battery life can be exhausted in almost 1 month. If the driver notices even minor malfunctions in the on-board electronics system, he should inspect the battery and determine the level of internal contents.
Level change during operation
Before you check the electrolyte level in the battery, you need to know how it changes during operation of the device. Over time, it constantly drops, regardless of whether an expensive battery was purchased or a cheap one. The speed of this process depends on the relay regulator. If this piece of equipment is faulty, the liquid will quickly boil away. Moreover, the timing of this process can be very short.
According to experts, when the voltage at the terminals increases to 14.5 V, if the relay-regulator is faulty, the electrolyte boils away in just a couple of days. The device will most likely require a complete replacement. It will not be possible to restore it.
If the battery gets very hot and splashes from boiling electrolyte appear, immediate action must be taken. When the voltage is high, air will escape from the fluid fill holes.
Electrolyte level determination
There are two ways to check the fluid level in a car battery. The first one is suitable for owners of batteries that have marks on the body. Two parallel lines indicate the minimum and maximum amount of solution inside the container. The condition of the electrolyte is visually assessed and a decision is made on further operation of the battery.
For devices that do not have such marks, there is another way to estimate the amount of solution. To do this, you need to use a glass tube (diameter 3-5 mm). Having opened any plug of the device, it is inserted into the safety shield until it stops. 
The hole that remains on the surface is closed with a finger. Next, the tube is removed from the battery and evaluated. The liquid remaining in it corresponds to the amount of electrolyte inside the test jar.
The column of the substance must be at least 11-15 mm. This procedure must be performed for all cans. If the level in some containers is insufficient, it is necessary to add the solution inside. When the level is above the specified value, the excess must be eliminated using a syringe or syringe.
Visual method
There is another approach to checking the electrolyte level in the battery. It is less accurate, but in the absence of available tools it will also work. To do this, you need to unscrew the plugs of the holes for filling the liquid. This must be done in good lighting. 
Looking inside the can, you should evaluate how the electrolyte comes into contact with the skirt from the holes down. In each of them the meniscus should be visible. This is the surface of the solution, which has a semicircular shape. The meniscus forms between closely spaced vessel walls.
Some battery models have a special indicator. You need to tap it lightly. This will make the color more visible. A green tint is normal. White color indicates the need to charge the device, and red indicates a lack of water in the container.
There are some rules that experts advise you to follow. These must be kept in mind when checking the electrolyte level in the battery. The basic rules boil down to understanding the operating principle of the device, as well as following safety recommendations.
If the battery has just been removed from charging, the electrolyte level will be high. This occurs due to thermal expansion. Also, hydrogen and air bubbles accumulate near the plates during the charging process. Therefore, experts say that the battery must cool completely. Otherwise the measurement will be inaccurate. 
All work is carried out using new rubber gloves. Just in case, you need to put a sufficient amount of clean water nearby. If electrolyte gets on your hands, it should be washed off immediately. For these purposes, water is required. It is also necessary to protect your eyes with special glasses. Following these simple recommendations will maximize the safety of your measurements.
Preparation of the solution
Having determined what level of electrolyte should be in the battery, you can take measures to restore the required value of the solution. If you need to add it to the container, you need to prepare the appropriate material.
The solution can be purchased or prepared independently. To create an electrolyte of the correct consistency, you need to prepare 1 liter of distilled water (sold in a pharmacy). You will also need 0.36 liters of sulfuric acid. It is prohibited to use tap water for such purposes. 
All components are poured into a plastic container. Everything needs to be mixed well. After this, the solution is closed with a tight lid and left for a day. Then you can use the prepared product.
Battery recovery
To pour the prepared solution inside, you need to unscrew the plug and put it on the fitting of the ventilation hole. The plug must be firmly placed on the corresponding hole. Next, the product is poured inside. The plug is screwed in and charging is performed.
Some drivers may be wondering how to restore their battery. The methods for carrying out this process are reduced to charging at low current. The procedure takes a long time, after which the density may increase slightly. Sulfuric acid can be poured inside only when the plates are in working condition.
By considering what level of electrolyte should be in the battery, as well as expert recommendations, you can restore the performance properties of the device being serviced.
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Checking the level and density in the battery
In principle, a battery is a simple thing. Does not require troublesome maintenance, but only if you operate your car as standard. Long trips on the highway, frequent ignition, temperature changes - all this affects the electrolyte level in the battery, and it must be checked periodically.
Battery operation
The operation of the battery (or battery for short) will be smooth if you remember about its service life. Nowadays they make batteries that become obsolete and require replacement. In theory, the only thing that is important is to periodically charge it and monitor the electrolyte level. The service life of the battery is extended if the device itself suggests this. For example, behind the battery there are plugs in the compartments of electrolyte-containing containers, which allows you to top it up. If there are no traffic jams, then the device has a special indicator that notifies you about the state of the battery - dull green or completely white color indicates that the device is dead.
An electrolyte is a liquid that creates a special environment that accumulates and distributes electricity through chemical reactions. Essentially, it is a solution of H2SO4 in H2O (sulfuric acid concentrate in distilled water).
The acid itself (maximum concentrated) is a fairly dense substance, 1.84 g/cm³, the electrolyte is 1.40 g/cm³. When sulfuric acid reacts with water, a lot of heat is released. If you use low-quality sulfuric acid, you can damage the battery.
It is important to know that the density of the mixture of sulfuric acid and water in the battery should vary from 1.07 to 1.30 g/cm³! If the density is higher or lower than the permissible limits, the battery will not work well and will not last long. The temperature of such liquid is +15°C.
Causes of battery problems:
- The battery may boil; if the temperature rises sharply, one of the components of the electrolyte - water - will simply evaporate.
- The generator may malfunction, the voltage will jump, which will contribute to improper circulation of electricity in the car charging device.
- The battery may discharge, especially if the machine is idle for a long time.
Checking the electrolyte level in the battery is a very important procedure. Because its too low level will dry out the internal plates, the cells will connect and the battery will be covered. And if the level is too high, then the outputs to the generator can oxidize and damage the entire system at once and for a long time.
Checking the electrolyte level in the battery.
There are two ways to determine the concentrate of the required liquid:
- By cell plugs,
- By eye (by magic eye).
Battery peephole
If we talk about the magic eye, then this is not an entirely accurate diagnosis and requires additional testing. You need to gently tap it (on this eye) and watch how the air bubbles rise. You will see the color indicator more clearly, and immediately use your analytical skills: Green - normal, White - requires recharging, Red - time to add water, acid has increased. There are other colors, but these are the most common in the Russian Federation.
It’s good if there is a scale on the charger body with a minimum and a maximum. Then you just look at the level of the solution and decide what to do.
The last method of checking is useful for clarifying the first and not being able to check with the second: take a glass tube, unscrew one of the plugs on the car charging body, push it inward to the fuse panel, plug the test tube with your finger, and pull it out. There will be electrolyte in the tube, if it is from 10 to 15 millimeters, everything is in order.
Measuring the electrolyte level with a tube
What electrolyte level should be in a car battery?
Hydrometer
As already mentioned, the permissible rate of this important solution ranges between 12 and 15 millimeters. Excess electrolyte can be filtered out using improvised means - a regular medical syringe or syringe. If there is not enough, we pour water. Just don’t add tap water! You will immediately ruin your charger. Water, firstly, must be distilled, and, secondly, its temperature must be in the range from +15 to +25°C. Water should be poured into a special hole - the filler neck - to the limit of the lower end of the tube. Once you fill it up, let it charge for three to four hours, and then we advise you to check the density of the resulting liquid so that the level of sulfuric acid corresponds to the permissible norm. The acceptable norm is 1.27-1.29 g/cm3. It is measured by a device called a hydrometer.
The question of how to measure the electrolyte level in a battery is not the first and most important. Next to it stands a second one concerning its density. If you haven’t added enough water, it’s a small matter, just add more, and in case of excessive dilution you will need a corrective
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What should be the density and level of electrolyte in a car battery?
Almost all car owners have an idea of what a battery is. However, few people know that it requires periodic maintenance and care. In the best case, the car owner simply charges the battery from time to time. But this is not enough. It is necessary to periodically check the electrolyte level in the battery banks and monitor its density. Moreover, if the density does not correspond to the norm, it needs to be adjusted. As for density, it is recommended to measure it after charging the battery. And the electrolyte level needs to be checked more often so that it does not drop too much. You especially need to monitor the level in the summer, when the temperature under the hood is high. In this material we will talk in detail about the level and density of electrolyte in a car battery.
What is put into a car battery?
Lead-acid car batteries of the WET group use an aqueous solution of sulfuric acid (h3SO4) as the electrolyte. There are also AGM batteries in which fiberglass is impregnated with electrolyte. And another type of lead-acid battery is GEL. In them, the electrolyte is transferred to a gel-like state using the addition of silicon oxide. The electrolyte level requires monitoring in WET car batteries. Everything said below is true for these batteries.
Electrolyte level in battery
So, let's say a few words about battery acid. Sulfuric acid has been used in the production of car batteries since their inception. 
Electrolyte for lead-acid batteries
Electrolyte for car batteries is sold in auto stores already in diluted form (density 1.29 g/cm3). In production, sulfuric acid has a higher concentration. It is obtained in 2 stages. First, the concentration is brought to 70%, and then 98%. In this form it is stored until used for various purposes. Car batteries are just a small area where sulfuric acid is used. It is used in various spheres of the national economy. Therefore, different grades of sulfuric acid are produced. They are given below (concentration and density are indicated in parentheses):
- Tower or nitrous (75%, 1.67 g/cm3);
- Contact (92.5─98%, 1.837 g/cm3);
- Oleum (104.5%, 1.897 g/cm3);
- High percentage oleum (114.6%, 2.002 g/cm3);
- Battery (92─94%, 1.835 g/cm3).
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The role of acid in a car battery
The previous section described what the electrolyte of a car battery consists of. Now let's talk about the role sulfuric acid plays in the operation of the battery. A car battery consists of a plastic case, lead plates of different polarities and an electrolyte in which they are immersed. The design of the plates provides for the presence of current-carrying lead grids. Depending on the type of battery, various alloying additives may be present in the grating material. The electrolyte in the housing is filled to a certain level, which will be discussed in more detail below.
Car battery design
The grids of the plates with a positive charge are coated with lead dioxide (PbO2). The plates with a negative charge are coated with lead powder (Pb). Sulfuric acid plays a key role in the electrochemical processes occurring in the battery. The basic parameters of the battery directly depend on the density of the electrolyte. Below are the reactions that occur when charging and discharging a car battery.
A reversible reaction occurs at the anode (positive electrode):
PbO2 + SO42− + 4H+ + 2e− ⇒ PbSO4 + 2h3O
At the cathode (negative electrode):
Pb + SO42− − 2e− ⇒ PbSO4
In the forward direction there is a discharge, in the reverse direction there is a charge of the battery.
The degree of battery charge can be determined by the density of the electrolyte. In a fully charged battery, the density of the banks ranges from 1.127 to 1.300 g/cm3. When the above reactions go in the forward direction, the acid in the car battery is consumed and the density of the electrolyte decreases. This process continues until the discharge current passes through the battery. The voltage at the battery terminals is maintained due to the process of diffusion of sulfuric acid to the electrodes from the solution.
Under real operating conditions, the discharge continues until the density decreases to 1.15 g/cm3. At this stage, the released lead sulfate completely clogs the surface of the active mass of the plates, and the diffusion process decreases. At this moment, the car battery voltage drops sharply.
The density of the electrolyte may change for another reason. In hot weather, the temperature under the hood can rise above 100 degrees Celsius. As a result of heating, the electrolyte level in the battery drops.
The volume decreases mainly due to the evaporation of distilled water. As a result, the density changes and, even worse, the plates are exposed. Therefore, it is necessary to monitor the level and add water.
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Density and electrolyte level in a car battery
Electrolyte level monitoring
The motorist is required to periodically monitor the electrolyte level in the battery. How it's done? In general, min and max marks are placed on the body of car batteries, which indicate the minimum and maximum levels, respectively.
Min and max labels
But using them for control is inconvenient. Most cases are made of black plastic, and it is impossible to see the level inside the battery. Therefore, to check the level, use a glass or plastic tube. You can simply take a transparent ballpoint pen or a straw from a juice box. Open the battery cans. Usually the plugs are made in the form of a single strip or are screwed individually.
One cap for all caps Separate caps for each jar
Lower the tube into each jar until it touches the plates. After this, pinch the top cut with your finger and remove it.
Electrolyte level measurement
There should be 10-12 mm of electrolyte left in the tube. This is a normal level. If less, you need to add electrolyte or distilled water. If the level is higher, then pump out the excess. A level that is too high is not as critical as a low level, but is also undesirable. In the outer banks, which are closer to the terminals, the level drops faster. If the level is low, you need to understand what to add, electrolyte or distilled water. To find out, you need to measure the density. This will be discussed below.
It is also worth saying a few words about measuring the electrolyte level in maintenance-free car batteries. They have no access to banks. Therefore, level control in them is carried out using marks on the case or a battery charge indicator. It is also called a hydrometer or “eye”. Return to content
Electrolyte density control
In the table below you can see the relationship between the degree of charge of the battery and the density of the electrolyte, as well as its freezing temperature.
| 1,11 | 11,7 | 8,4 | 0 | -7 |
| 1,12 | 11,76 | 8,54 | 6 | -8 |
| 1,13 | 11,82 | 8,68 | 12,56 | -9 |
| 1,14 | 11,88 | 8,84 | 19 | -11 |
| 1,15 | 11,94 | 9 | 25 | -13 |
| 1,16 | 12 | 9,14 | 31 | -14 |
| 1,17 | 12,06 | 9,3 | 37,5 | -16 |
| 1,18 | 12,12 | 9,46 | 44 | -18 |
| 1,19 | 12,18 | 9,6 | 50 | -24 |
| 1,2 | 12,24 | 9,74 | 56 | -27 |
| 1,21 | 12,3 | 9,9 | 62,5 | -32 |
| 1,22 | 12,36 | 10,06 | 69 | -37 |
| 1,23 | 12,42 | 10,2 | 75 | -42 |
| 1,24 | 12,48 | 10,34 | 81 | -46 |
| 1,25 | 12,54 | 10,5 | 87,5 | -50 |
| 1,26 | 12,6 | 10,66 | 94 | -55 |
| 1,27 | 12,66 | 10,8 | 100 | -60 |
Like the level, density must be periodically monitored. It is best to do this after the battery is fully charged. On a fully charged battery, the density should be 1.29 g/cm3. In regions where winter temperatures are low, it is recommended to maintain a density of about 1.3 g/cm3. To measure density you need a device called a hydrometer. In stores it is sold at a price of 150-200 rubles.
Hydrometer
In order to measure the density, lower the hydrometer into the jar and use a bulb to draw electrolyte into the flask. The special float scale inside will show the density. In this way, you measure the density in all jars and calculate the average value. It should be approximately 1.29 g/cm3.
If the level is low and the density is higher than normal, then simply add distilled water. It is also sold in automotive stores and is inexpensive. If the level is normal and the density is high, then take some of the electrolyte from the cans and fill it with water. This operation must be done for each battery cell, since the banks do not communicate with each other.
Distilled water
If the density of the electrolyte on a charged battery is below 1.29 g/cm3, then it will be more difficult to bring it back to normal. You need to select the solution from the jars using a “pear” or a hydrometer. Instead, fill in fresh electrolyte of the required density. It may be necessary to completely replace the electrolyte in the car battery.
The electrolyte is a mixture of sulfuric acid and distilled water. It is an integral part of any battery. It is very important to monitor its condition and level and, if necessary, top up or change. Otherwise, the battery may fail.
Contents
Why is electrolyte needed in a battery?
Lead-acid batteries undergo electrochemical processes that produce electricity. These processes are possible only with the direct participation of the electrolyte.
The battery has negatively and positively charged plates. They contain lead conductive elements. They may have various additives, which determine the type of battery.
The degree of charge of the battery depends on the density of the electrolyte. If it is increased, the battery will be overcharged, and an aggressive environment can generally harm the battery. When it is lowered, the battery will be discharged. The density of concentrated battery acid is 1.835. In order to bring the value to normal, it is necessary to use distilled water.
The range of indicators for a normally charged battery is within 1.23 – 1.25 g/cm3. When the engine starts, the audio and light elements are turned on, the battery discharges. This happens due to the occurrence of an electrochemical reaction. The substance loses sulfuric acid, resulting in a drop in density and discharge of the battery.
How much electrolyte should be in the battery
The car owner must constantly monitor the electrolyte level. If it drops, you will need to add distilled water. Depending on the battery capacity, the volume of the mixture will depend:
- 55 Ah – 2.5 l;
- 60 Ah – 2.7-3 l;
- 62 Ah – about 3 l;
- 65 Ah – about 3.5 l;
- 75 Ah – 3.7-4 l;
- 90 Ah – 4.4-4.8 l;
- 190 Ah – about 10 liters.
Depending on the manufacturer, technology and model, these figures may vary, so they are conditional. The main thing to remember is that the electrolyte must completely cover the plates by 10-15 mm and in no case should they protrude.
Battery cover sensor How to check the electrolyte level in a battery
Most batteries on the banks have a scale with MIN and MAX values, and it is in this range that the electrolyte should be. There are models with plastic tabs under the stoppers that go down inside the cans; they should be immersed in the liquid by 5 mm.
Modern batteries are equipped with a special sensor on the case, which indicates a low electrolyte level and the degree of discharge of the battery.
If for some reason there are no symbols, then you can resort to the following method:
- Take a small, clean tube;
- Wipe the battery case clean and dry;
- Unscrew the lids from all the cans;
- We lower the tube into the jar at a right angle and touch its plates;
- Press the top hole of the tube tightly with your finger;
- Carefully pull out and measure the height of the liquid (should be at the level of 10-15 mm);
- We repeat the procedure with all banks.
If there is not enough mixture in the jars, you will need to add distilled water. You need to top up until the plates are completely closed. Distilled water can be purchased at a pharmacy. You cannot use regular tap water.
If you operate a car with “bare plates,” they will quickly crumble and fall apart.
There are now maintenance-free batteries on the market. If there are no lids on the body, then you will not be able to add water into it.
Why might electrolyte levels drop?
If the battery is not hermetically sealed, the liquid will slowly evaporate and boil away. Therefore, it is necessary to periodically add distilled water.
Also, when charging, the mixture always boils, so after each charging it is recommended to measure the electrolyte level. First you need to wait until the electrolyte stops boiling.
What can you add water or electrolyte to the battery?
If the battery plates are not closed, it means that the level of the substance is not high enough and you need to add distilled water. At the same time, you cannot fill in plain water, since it contains various impurities that can disrupt the operation of the battery and cause it to fail.
If the mixture has sufficient density, then distilled water is added. If it approaches the lower mark, then you can add the alkaline mixture. When current passes through the battery, acid is consumed. The process is called diffusion of H2SO4 between the volume and the electrode. This maintains voltage at the battery terminals.
As practice shows, not everyone who is interested in the question of how much electrolyte is in a battery knows what an electrolyte is and why it is needed, so now you will receive answers to all the questions raised. So, first things first.
What is an electrolyte and why is it needed at all?
An electrolyte is a solution of sulfuric acid and simple distilled water. Lead-acid batteries are filled with it in the required concentration and volume so that, thanks to the chemical processes occurring with this solution, they can store energy. Hence, if the concentration or amount of electrolyte in the battery decreases, it ceases to fully cope with its duties and begins to need replacement or restoration. In the latter case, motorists are faced with the question: how much electrolyte should be in the battery.
So, how much electrolyte should be in the battery?
How much electrolyte a car battery must contain to operate as efficiently as possible is directly determined by its capacity. Of course, depending on the manufacturer, some variation is possible, but in general, the volume of electrolyte for batteries of different capacities will be as follows:
- 55 Ah – 2.5 l +/- 100 g;
- 60 Ah – 2.7-3 l;
- 62 Ah – about 3 l;
- 65 Ah – about 3.5 l;
- 75 Ah – 3.7-4 l;
- 90 Ah – 4.4-4.8 l;
- 190 Ah – about 10 liters.
But this is only an approximate displacement; it is needed more for reference before going to the store. In the process of restoring the battery, you need to focus not on it, but on the special marks present on the body of the latter. Now more details.
What should be the electrolyte level in the battery?
If your battery has a scale with a minimum and a maximum, then the question of what level the electrolyte should be filled to can be solved very simply - along the top line, that is, to the “MAX” mark,
If there is no such scale, perhaps there are “tongues” in the holes of your battery, then you need to pour enough electrolyte into the battery so that they are covered with a 5 mm layer of solution (completely immersed in it).
Well, if you have neither one nor the other, fill the battery with electrolyte in the volume recommended above (it should not be full, but a little less), and then for self-control, take a glass tube with a diameter of up to 5 mm and lower it inside the battery, until it hits the safety shield. Close the top hole of the tube with your finger and take it out. If the level of electrolyte remaining in it is within 10-15 mm, you have done everything correctly - the electrolyte level in the battery is optimal.
