Battery discharge is the most important mode of battery operation, in which consumers are provided with current. The process of battery discharge is described by an electrochemical reaction:

Lead sulfate and water are formed, so as the battery discharges, the density of the electrolyte decreases.

The nature of the discharge depends on many characteristics describing the condition of the battery and external factors. The entire variety of battery discharge modes is described by a relatively small set of discharge characteristics.

Battery discharge characteristics

The main discharge characteristics are the following values ​​that change during the discharge time at a constant normal discharge current:

• - resting emf - emf that changes linearly during the discharge process from 2.11 V to 1.95 V;
• - electrolyte density - varies from 1.28 to 1.11 g/cm3;
• - battery voltage: initial is 2.11 V, final discharge voltage is 1.7 V;
• - discharge current;
• - discharge capacity of the battery.

The first three characteristics do not require further explanation. Let's focus on the last two.

Discharge capacity is the amount of electricity released by the battery when discharged.

However, the battery capacity depends on the discharge conditions. Therefore, the very concept of capacity is associated with discharge conditions. This concept of capacity is a comparative characteristic.

The discharge capacity of a battery is the amount of electricity supplied by the battery when discharged by normal current.

The normal discharge current is the 10-hour discharge current.

Along with this, the value of the discharge current of the 20-hour discharge mode is used. Most manufacturers indicate the battery capacity in a 20-hour discharge mode.

On the graphs of voltage versus time during discharge with a constant current, a decreasing almost straight line is observed, and at the end of the discharge the voltage decreases linearly and quickly. The battery should not be discharged below 1.7 V.

The degree of battery discharge can be characterized by the relative residual capacity.

Relative residual capacity is defined as the amount of electricity that a battery is capable of delivering at normal discharge current, starting at a given point in time, divided by the capacity of the same serviceable and fully charged battery.

Qrest. rel. fairly fully characterizes the energy state of the battery at the moment of operation.

For example, if the battery is not worn out, has the highest capacity and is fully charged, then Qres. = Qmax.

and therefore the battery has a residual relative capacity of 100%.

However, for example, if the battery is heavily sulfated, it charges up to 2.7 V with intense gas evolution (fully charged) and is able to discharge at normal discharge current.

Of course, the relative discharge capacity of a battery depends on many factors that determine the condition of the battery at the current time of operation. This is basically:

• - battery charge level;
• - electrolyte density;
• - electrolyte temperature;
• - charge mode.

A strict and correct correspondence between these charging and discharging characteristics is necessary. Therefore Qrest. rel. - an important diagnostic characteristic. Knowing it, you can avoid supercritical, emergency operating modes of the battery.

For example, if Qrest. rel. = 75%, and the electrolyte temperature is 25 C, then the starter operating mode of the battery is already supercritical, i.e. The density of the electrolyte must be strictly determined at a given temperature and state of charge of the battery. The battery must be fully charged without overcharging or undercharging.

Select the discharge mode in accordance with the condition of the battery (this condition is often violated, especially in the cold season, when using the starter for a long time in an attempt to start a particularly faulty engine). If you neglect this, you can defrost the battery or some of its (most discharged) batteries.

Thus, knowing the main discharge characteristics of the battery, their interdependence and impact on the residual capacity of the battery, you can protect the battery from premature wear and failure.

Let us recall once again the main negative discharge factors that sharply reduce battery life:

• - deep discharge;
• - constant undercharging mode;
• - non-compliance with the standard electrolyte density;
• - sulfation of the plates;
• - excessive (supercritical) discharge currents.

The discharge capacity of the battery is influenced by the density of the electrolyte. However, the concentration of sulfuric acid in starter batteries is not determined by considerations of obtaining maximum capacity, but is associated with other factors: service life, self-discharge current, performance at low temperatures.

Therefore, you should adhere to the basic rules: the battery must be fully charged (preferably with reverse current), and the electrolyte concentration corresponds to the established norm.

The discharge capacity of a battery strongly depends on the discharge current and electrolyte temperature. In most cases, manufacturers indicate the battery capacity for a 20-hour discharge mode at T = 25 C. That is, discharge current, for example, of a battery with a capacity of Q=60A. h is equal to

Iр = 60/20 = 3A

However, the same battery has a discharge capacity at a current of 200A (starter discharge mode) of no more than 20 Ah. That is, in this mode, the battery discharges below the permissible values ​​over time

Tr = 20/200 = 0.1 hour = 6 minutes

As the temperature drops, the discharge capacity of the battery also decreases greatly. This largely depends on the design of the battery, however, most batteries, for example, at - 10 C have a capacity 2 times less than at +25 C. This explains the difficulty in cranking the crankshaft with the starter in winter conditions (in addition to the increased mechanical load due to thickening lubricants).

Discharge characteristics make it possible to determine the condition of the battery and prevent its operation beyond the permissible characteristics.

The modes of deep (lower than practical at U=1.7V) discharge and systematic undercharging are especially unacceptable. In this case, the starter discharge currents quickly destroy the plates. The degree of discharge of the battery can be determined by the density of the electrolyte.

When checking a battery with a load fork, you can determine the degree of discharge of each battery depending on the voltage.

The rechargeable battery is the most important component of backup and autonomous power supply systems for individual electrical appliances or entire industrial and domestic facilities. Today, lead-acid batteries (AGM VRLA and GEL VRLA), OPZS, OPZV, as well as nickel-cadmium (Ni-Cd) and lithium-ion types (Li-ion, LiFePO4, Li-pol) are widely used.

The emergence of chemical power sources began back in 1800, when the famous Italian scientist Alessandro Volta placed plates of copper and zinc in acid and obtained a continuous voltage (Volta column). Modern lead-acid batteries, as the name suggests, consist of lead and acid, where the positively charged element is lead and the negatively charged element is lead oxide. The most common rechargeable battery consists of six 2V cells and has a total voltage of 12V.

Battery Specifications

The quality of batteries can be determined by several important properties:

Capacity, Ampere/hour;

Voltage, Volt;

Permissible discharge depth, %;

Service life, years;

Operating temperature range, °C;

Self-discharge, %;

Dimensions, mm;

• Charge current, A;

Advice! i> Be sure to take into account that all battery characteristics given by the manufacturer are indicated for a temperature of 20 - 25 ° C; with a decrease or increase in the ambient temperature where the battery will be used, the performance indicators change, as a rule, they decrease.

Battery capacity

This parameter reflects the amount of energy that the battery can store, measured in Ampere hours. Currently in Ukraine you can buy batteries with capacities from 0.6 to 4000 Ah. For example, a battery with a capacity of 200Ah is capable of powering a load with a current of 2A for 100 hours, or a current of 8A for 25 hours, etc. Be sure to keep in mind that as the current consumption increases, the capacity of the battery will decrease, which is why manufacturers indicate the capacity with an additional parameter - C.

An additional, but very important characteristic is marked with the Latin letter “C” with a numerical parameter, usually from 1 to 48 hours and indicates the capacity of the battery when discharged in a certain period of time (C1, C5, C10, C20, etc.) . The C10 value is considered to be the standard value and the vast majority of manufacturers indicate the capacity at a 10-hour discharge. For example, a capacity of 100Ah at C10 means that the battery will provide this capacity with a 10-hour discharge, the same battery at C5 will have a lower capacity - 80Ah at C5, and if the discharge occurs over 20 hours, the capacity will increase and amount to about 115Ah at C20. Thus, when choosing the battery capacity, it is necessary to take into account the time during which the discharge will be carried out, this is of great importance.

Figure No. 1.

Advice! Please note that some manufacturers and distributors may indicate the capacitance value at C20. This is done to artificially inflate the indicator while keeping the cost of the battery unchanged.

During operation, the capacity will gradually decrease; this is a natural process of “aging” of the battery, which occurs due to a decrease in the density of the lead plates and partial loss of primary lead from the positive and negative plates. High intensity of use and deep discharges will lead to rapid wear of the positive and negative plates of the battery and its failure. To prevent this from happening, it is necessary to provide a reserve supply of capacity. To increase the capacity of the battery cabinet, several batteries with parallel connection are used.

Battery voltage

Voltage level is a key characteristic based on which a battery is selected. Today, cells and batteries with the following voltage values ​​are common: 1.2, 2.4, 6, 12V. A battery bank with a higher voltage (24, 48, 96V, etc.) is assembled using several 12V batteries with a serial connection type.

By measuring the voltage level, you can assess the state of charge and the degree of wear of maintenance-free types of batteries (AGM and GEL VRLA). The voltage measurement is carried out over several hours when the battery is completely idle and disconnected from the charger. The normal level for AGM batteries is considered to be from 13 to 13.2V.

Allowable discharge depth

Different types and subtypes of batteries have recommended discharge depth parameters. Below is table No. 1, which shows the most common characteristics of batteries with permissible and recommended depth of discharge.

Battery Type

Table No. 1. Values ​​of permissible and recommended battery discharge values.

The level of discharge is a key factor in the service life of the battery, along with the intensity of use. Even the most expensive and high-quality lead-acid battery can be destroyed in 7-10 days if a full 100% discharge to a voltage of 9V is performed several times in a row.

The most resistant to deep discharges are lithium-ion and nickel-cadmium, as well as specialized lead-acid batteries, which have been optimized by the developers for deep discharges. Typically, such series contain the word “Deep” in the title, which means “Deep”.

Battery life

Modern lead-acid batteries are optimized for a variety of operating conditions. Some have a shorter service life, but provide a higher discharge characteristic, others have a longer service life, but are suitable for rare discharges and operation in buffer mode, etc. Therefore, if the manufacturer indicates a service life of 10 years, this information corresponds to the ideal operating mode, when not the cyclic life and, more importantly, the depth of discharge are exceeded. Let's give an example: if the manufacturer indicated that the battery life is 10 years and the number of charge/discharge cycles allowed is 600 with a depth of 50%. The battery can serve the specified period under ideal operating conditions and no more than five cycles per month. This mode fully corresponds to the buffer type.

The service life depends entirely on the number of charge and discharge cycles completed, and also depends on the environment where the battery is installed. As noted above, the more the battery is discharged and the longer it is in a discharged state, the less it will last. The higher the ambient temperature, the more active the chemical reaction takes place and the more susceptible the lead plates are to destruction.

Table No. 2 shows approximate values ​​of the service life and cyclic resource of batteries depending on their types. The data corresponds to an optimal operating temperature of 20 – 25°C.

Battery type	Cyclic life at depth of discharge				Service life, years

Table No. 2. Resource depending on the type of battery.

Figure No. 2.

Operating temperature range

With the exception of the lithium-ion type, which uses the mineral lithium, the operating principle of batteries is based on chemical elements and the interaction between them. Therefore, almost all the main characteristics of batteries depend on the ambient temperature. As a rule, as the temperature increases, the service life decreases, and if the temperature is above ~35 ° C, the service life of lead-acid AGM batteries will be halved.

The ambient temperature level also affects the available battery capacity. As the temperature drops, the capacity drops. At –20°C, the battery capacity will decrease by 30–40% of the nominal value.

Figure No. 3.

Figure No. 4.

Battery self-discharge

Self-discharge is a characteristic phenomenon for batteries of all types. This indicator reflects the degree of spontaneous loss of capacity during idle time after a full charge. The self-discharge characteristic is indicated as a percentage over a certain period of time, most often per month.

As an example, consider a 100Ah AGM VRLA battery that has been fully charged and not used for a month. The average self-discharge value for AGM VRLA type is about 1.5%, respectively, after a month the capacity will be about 98.5 Ah.

Self-discharge rates are influenced by ambient temperature. As the temperature rises, the indicator will increase. The cause of self-discharge is the release of oxygen molecules on the electrode of a positive charge, and an increase in temperature is a catalyst for this process.

Figure No. 5.

Charge current

The current used to charge the battery directly depends on the capacity of the battery being charged. Lead-acid batteries are charged with a current of 10–30% of the rated capacity; depending on the system, less powerful chargers can be used.

Attention! You cannot charge batteries with high current; this leads to irreversible chemical reactions and significantly reduces the performance characteristics of the battery.

Figure No. 6.

Dimensions and weight of batteries

Depending on the capacity of the batteries, the dimensions and weight vary, with rare exceptions there may be changes in size for the same capacity. There are generally accepted sizes of small batteries up to 250Ah, which are used as built-in power supplies for uninterruptible power supply systems, children's toys, golf carts, scrubber dryers, etc. Depending on the manufacturer, the connecting dimensions may vary from tenths to several millimeters.

Advice! Pay attention to the height of the battery without terminals and with terminals; some manufacturers indicate two heights.

The concept of battery capacity

The capacity of the battery is one of its most important technical characteristics. This term is understood as the amount of time that a source of autonomous energy is capable of powering the electrical consumers connected to it. In other words, this is the maximum amount of electricity accumulated by the battery during a full charging cycle. The unit of capacity is Ah (ampere-hour), for small batteries it is mAh (milliamp-hour).

An example of calculating the required capacity

As you know, the calculation of power consumption is made in W, and the battery capacity for a UPS is in Ah. To calculate the required battery capacity to power a particular equipment, it is necessary to make some recalculation. For a better understanding, let's look at a specific example. Let's say there is a 500 W critical load that requires backup for 3 hours. Since the amount of accumulated energy depends not only on the battery capacity, but also on its voltage, to calculate it we divide the total power of the redundant equipment by their operating voltage (often confused with the open circuit voltage of a fully charged battery). For a standard 12V battery, the required battery capacity will be:

Q= (P t) / V k

where Q is the required battery capacity, Ah;

V – voltage of each battery, V;

t – reservation time, h;

k is the coefficient of battery capacity utilization (the amount of electrical energy allowed for use by consumers).

The need to introduce a coefficient is due to the possibility of an incomplete charge of the battery. In addition to this, a strong (deep) discharge following a small number of charge and discharge cycles leads to premature wear and failure of the battery. For example, if a new battery is discharged to 30% of its total capacity and then immediately charged, it can withstand about 1000 such cycles. If the discharge value decreases to 70%, the number of these cycles will decrease by approximately 200.

In total, we find that to power this load for the specified period of time it will be necessary:

Q= 500·3/ 12·0.7 = 178.6 Ah.

This is the minimum required battery capacity for the case under consideration. Ideally, it is better to take an energy source with a small reserve (about 20%) so as not to completely discharge it each time - this will help maintain battery performance for as long as possible.

Q = 178.6 1.2 = 214.3 Ah.

This means that to solve this problem it is necessary to purchase batteries with a total capacity of at least 215 Ah. When using a UPS in conjunction with a generator, it is recommended to reduce the capacitance correction factor to 0.4, since in such a combination batteries are most often used to maintain continuous power supply until the power plant turns on and the entire load is switched to it. Moreover, if the value of the coefficient 0.4 includes the loss of battery capacity during its aging, due to the peculiarities of the pulse converter and others, then on average the discharge of the battery can reach 50% of its nominal capacity.

In the case when several batteries are used to back up the load, the amount of energy accumulated in them is absolutely independent of the type of their connection - parallel, serial, or mixed. Taking into account this feature, it is necessary to substitute the voltage of one battery into the formula for determining the total capacity of batteries, but in this case it is allowed to use only batteries with the same technical characteristics.

Indicators of batteries, with which the concept of capacity is inextricably linked

1. Dependence of battery capacity on its discharge current.

This dependence is based on the following fact: when the protected load is connected to the battery without using a converter, the amount of current consumed by the battery remains unchanged. In this case, the operating time of connected electrical consumers will be determined as the ratio of the selected capacity to the consumed current. In a more familiar form, this formula is written as follows:

where Q is the battery capacity, Ah (mAh);

T – battery discharge time, hours.

If we are dealing with large amounts of current consumption, then the actual power indicators are often lower than the nominal ones indicated in the passport.

1. Dependence of battery capacity on energy

Today, it is quite common among users that the capacity of a battery is a value that fully characterizes its electrical energy, accumulated by the battery when it is 100% charged. This statement is not entirely correct. Here it is also necessary to make a reservation that the battery’s ability to accumulate energy directly depends on its voltage and the higher it is, the more energy the battery can accumulate. In fact, electrical energy is defined as the product of the charging current, battery voltage and the flow time of this current:

where W is the energy accumulated by the battery, J;

U – battery voltage, V;

I – constant battery discharge current, A;

T – battery discharge time, hours.

Based on the fact that the product of current and charging time gives us the battery capacity (as discussed above), it turns out that the electrical energy of the battery is found by multiplying the rated voltage of the battery and its capacity:

where W is the energy accumulated by the battery, Wh;

Q – battery capacity, Ah;

U – battery voltage, V.

When several batteries of the same capacity are connected in series, the total indicator of this bundle is equal to the sum of the capacities of all batteries included in its composition. In this case, the energy of the resulting battery pack will be determined as the product of the electricity of one battery and their number.

1. The concept of battery energy capacity

An equally useful indicator of rechargeable batteries for the consumer is their energy capacity, measured in units such as W/cell. This concept characterizes the battery’s ability for a certain short period of time, which most often is no more than 15 minutes, in constant power mode. This indicator is most widespread in the United States, but recently it has been gaining popularity among consumers in many other countries. To approximate the calculation of the battery capacity, measured in Ah based on its energy capacity in W/cell for a period of 15 minutes, use the formula:

W – energy capacity of the battery, W/cell.

1. The concept of battery reserve capacity

For car batteries, another characteristic is distinguished - reserve capacity, which indicates the battery’s ability to power the electrical equipment of a moving car when the vehicle’s standard generator is not working. This parameter is also better known in the USA and is called “reserve capacity”. It is measured in minutes of battery discharge with a current value of 25 A. To approximate the nominal capacity of the battery based on its reserve capacity indicator, indicated in minutes, you must use the formula:

where Q is the battery capacity, Ah;

T – battery reserve capacity, min.

Battery capacity and charge (charge)

Another fairly popular misconception is the identification of the concepts of battery capacity and its charge (charge). Let's dot the i's. Capacity refers to the maximum potential of a battery, that is, the amount of energy that it can accumulate in a fully charged state. The charge, in turn, represents this energy necessary to power the load in autonomous mode. Hence the conclusion is that the amount of charge of the same battery can be different depending on the charging time of the battery, and the amount of its capacity in the discharged and charged state is the same. Here we can draw an analogy with a glass into which water is poured. The volume of the device will represent the capacity - this is a value that does not depend on whether the glass is full or empty, and the water that is poured is the charge.

What other factors does the battery capacity depend on?

Discharge current

The battery capacity indicators that can be found in their technical documentation and on the product case are indicated by the manufacturer based on the results of test measurements made according to the above formula (Q = I T) at a standard discharge duration (10, 20, 100 hours, etc.). d.). The capacitance is designated accordingly - Q10, Q20 and Q100, as well as the discharge current - I10, I20 I100. In this case, the amount of current flowing through the load with a discharge time of 20 hours will be determined by the formula:

Following this logic, we can assume that during a discharge lasting a quarter of an hour (15 minutes), the current will be equal to Q20 x 4. However, this is not the case, as practice shows; in the case of a 15-minute discharge, the capacity of a standard lead battery will be no more than half of its rated capacity . Accordingly, the value of the parameter I0.25 will be slightly less than Q20 x 2. From here we can conclude that characteristics such as time and discharge current are not proportional to each other.

Final discharge voltage

Each time the battery is discharged, the voltage on it gradually drops, and when the so-called final discharge voltage is reached, it is imperative to disconnect the battery. Moreover, the lower this characteristic, the correspondingly higher the actual battery capacity will be. As a rule, manufacturers indicate on their own batteries the minimum value of the final discharge voltage, which in turn depends on the current used to discharge the battery. There are situations when the voltage of the energy source drops below this value (they forgot to turn off the battery in time or this could not be done because it was impossible to de-energize the load for a long period). Then a phenomenon called deep discharge of the battery occurs. If the battery is often allowed to be deeply discharged, it can quickly fail.

Battery wear

As is generally accepted, a new battery has a nominal capacity (the one indicated by the manufacturer). However, the actual value of this indicator may differ slightly - be less than declared due to long-term storage in a warehouse, or after several full charge and discharge cycles and short-term operation in buffer mode, it may increase slightly. Further use of the battery, as well as its storage, invariably leads to physical wear and tear of the energy source, its aging and gradual failure.

Temperature

Such an important factor as the ambient temperature in the place where the battery is used greatly affects the capacity of the latter. If the temperature increases from 20°C to 40°C, the battery capacity increases by 5%, and when it drops to 0°C, it decreases by an average of 15%. A further decrease in air temperature leads to a drop in this parameter by another 25% relative to the nominal value.

How to check battery capacity?

Very often, the owner of a used battery is faced with the task of determining its residual capacity. The classic and, to our credit, the most reliable and effective way to check the actual capacity of a battery is considered to be a test discharge. This term refers to the following procedure. The battery is first fully charged, after which it is discharged with direct current, and the time during which it is completely discharged is measured. After this, the battery capacity is calculated using the already known formula:

For greater calculation accuracy, it is better to select the value of the constant discharge current so that the discharge time is about 10 or 20 hours (this depends on the discharge time at which the nominal battery capacity was calculated by the manufacturer). Then the obtained data is compared with the passport data, and if the residual capacity is 70-80% less than the nominal capacity, the battery must be replaced, since this is a clear sign of severe wear of the battery and its further wear will occur at an accelerated pace.

The main disadvantages of this method are the complexity and labor-intensive implementation, as well as the need to remove batteries from service for a fairly long period of time. Today, most devices that use rechargeable batteries for their operation have a self-diagnosis function - a quick (in just a couple of seconds) check of the condition and performance of energy sources, but the accuracy of such measurements is not always high.

A car battery is a very important element, despite the simplicity of its design, it is fraught with several incomprehensible abbreviations, such as capacity, and of course starting current. I have already written about some, I will write about some more, but today we will talk about the “starting indicators” of the battery - why this is so important and what they should be. Not everyone knows about this parameter and often when choosing a new battery, they initially make a big mistake! And it leads to the fact that the battery quickly fails and cannot start your car in winter...

To begin with, the definition

Battery starting current (sometimes called starter current) - this is the maximum value of the current required to start the engine, namely to power the starter so that it can turn the flywheel with the pistons attached to it. This process is complex, because the pistons compress the fuel (9–13 atmospheres), which enters the chambers. Winter starting is even more difficult, because the oil thickens and the starter needs to overcome not only compression, but also the lack of normal lubrication of the cylinders.

What is the main purpose of a car battery? Of course, the accumulation and subsequent start of the engine, it seems like the structure of many models is the same, but the characteristics are not the same. No, of course, the charged model will have approximately 12.7V, but the current strength and capacity will differ.

A few words about the structure and properties

Batteries were created specifically to recharge and start the car, that is, they are very practical from the point of view of operation. A regular battery discharged very quickly, and it was expensive to change it, which is when batteries were invented.

Through trial and error, batteries evolved - so a few years after the invention, a very specific model emerged, this was about 100 years ago, which has not changed until now.

Usually these are six compartments with plates made of lead (negative) and its oxide (positive), which are filled with a special electrolyte made of sulfuric acid. It is this combination that makes the battery work; if one component is excluded, the operation will be disrupted. One scattered battery generates an average of 2.1V, this is extremely little to start the engine; in an average battery, they are combined by connecting them in series, usually 6 banks of 2.1V = 12.6 - 12.7V. This voltage is enough to excite the starter winding.

A few words about capacity

However, voltage is only one of the components; it is unified, that is, it is the same for all batteries, regardless of capacity.

But the capacity can differ significantly. It is measured in Amperes per hour, or simply Ah. If we derive a small definition, then this is the ability of a battery to deliver a certain amount of current for an entire hour. Automotive options start at 40 Ah and go up to 150 Ah. However, the most common ones on ordinary foreign cars are 55 – 60 Ah. That is, the battery can deliver 60 Amps for an hour, and then it will be completely discharged. To be honest, this is a big value, if you multiply 12.7 (voltage) and 60 Ah (capacity), you get 762 Watts per hour! You can warm up the electric kettle a couple of times.

We also sorted out the capacitance, now let’s talk directly about the starting current.

So what is this inrush current?

As I already wrote above, the starting current is the maximum current that the battery can deliver in a very short period of time. In simple words, to start the engine of an average car you need approximately 255 - 270 Amperes, a lot! In essence, these are “starting values”, from the word “start” in relation to the power unit.

If the battery capacity is approximately 60 Ah, then this exceeds its nominal value by approximately 4 - 5 times. True, such tension should only be given for about 30 seconds, no more.

Often in the southern regions of our country, where the air temperature always remains in the positive zone, this parameter is not even considered! Because no matter what, we take an average battery, and it will cope with its duties perfectly. After all, it’s warm outside and the oil is liquid. But in the northern regions this indicator is one of the most important, where temperatures are often in the extremely negative zone and it is difficult to start the power unit; the oil looks more like jelly than a flowing liquid. The launch will be extremely difficult.

If to start the engine at “+ 1 + 5” degrees, 200 - 220 Amperes will be enough (at one time), then to start it already at - 10 - 15 degrees, you need to spend 30% more energy, and this is 260 - 270 Amps. Now think about how much energy is wasted at -20 - 30 degrees Celsius.

Thus, the lower the temperature in winter, the more important this parameter is, this is a kind of axiom.

What does the starting current depend on?

If you look at different manufacturers, for example European countries, the USA, Russia or China, then all these batteries will have different inrush current ratings. So, for example, if you compare 55 Ah China and Europe, the difference can be 30 - 40%! But why is that?

It's all about technology:

• The use of purified lead, even in simple acid batteries, will lead to rapid charging and subsequent discharging, and accordingly the starting values ​​will increase.
• A larger number of plates in a body of the same dimensions.
• More electrolyte.
• The plus plates are more porous, which will allow more charge to accumulate.
• Hermetic designs do not allow the electrolyte to evaporate, which will allow the battery to always maintain the desired level without exposing the plates.

Of course, you can add build quality and integrity of the manufacturer, all this gives better results than competitors. It’s true that such batteries are more expensive.

But at the moment, there are also new technologies - the record holders for the return of starting current are, their return current can reach up to 1000 Amperes in 30 seconds, about 3 - 4 times more than that of conventional acid options. Although these technologies also have their disadvantages, and first of all this is the price.

It is also worth noting that when starting the engine, the battery voltage drops to approximately 9 Volts, but the current increases many times - this is a normal process. After starting the engine, the voltage will return to its normal level of 12.7 Volts, and the spent charge will be replenished by the car’s generator. If the voltage readings during startup drop to 6 Volts (and take a very long time to recover), then this can be critical; the starter simply does not have enough energy to start. Most likely the battery is failing.

How are measurements taken?

After the battery is produced, it must be tested to determine the starter voltage. Tests in production are complex; batteries are often placed in subzero temperatures, cooled for several hours, and then tried to start the engine.

Usually the tests take place at -18 degrees Celsius and the start-up lasts 30 seconds; if the battery copes, then it can be put into production. If not, change the design, filling, and carry out tests on a new one.

They measure several times, that is, there are a number of intervals with maximum values, during such intervals the maximum currents that this particular instance is capable of producing are measured, they are recorded and later applied to the “sides” of the battery. It should be noted that not all batteries in the batch are tested so strictly. However, “defects” are present, and checks are carried out with a load fork.

To be fair, it is worth noting that earlier in Soviet times, batteries were not filled with electrolyte at all in production (there was a concept of dry charge), you had to fill and charge them yourself! That is, we buy an electrolyte of the required density, and then charge it for 12 – 24 hours.

What is the starting current of an average battery and what should I do if I buy a larger one?

At the moment there is a division of starting values ​​into gasoline and diesel units. After all, a diesel engine initially needs a higher indicator, because its compression ratio is much higher, can reach up to 20 atmospheres.

SO, the averages:

For gasoline options this is 255 Amperes

For diesel options - at least 300 Amperes

These figures, as they say, were measured at minus 18 degrees Celsius, which may not be enough when starting in severe frosts.

But now, with the development of technology, often in stores we can see starter current indicators of 400, 500 and even 600 Amperes! What happens if you take these numbers? Am I burning my starter?

The answer is simple - of course not. Don't burn it! Take it and forget what a cold start is, with such characteristics you won’t care about any frost.

As for the starter, with a higher current, it will rotate faster and stronger, which will allow it to make more revolutions, and in turn this will contribute to a quick and high-quality start of the engine.

Of course, you need to read the characteristics of your car, but I think a starting value of 450 - 500 AMPERES will be enough for all regions of Russia. Again, I’ll make a reservation, I’m now considering ordinary cars, not trucks, with large and high-volume engines; often even 600 will not be enough for them.

Classification in the world

As I have already touched on a little, in the world there are now several main classifications of inrush current values. Which have their own identification and labeling methods. To begin with, how are they marked:

• German manufacturers stand out here - they apply the “DIN” marking
• In America they apply “SAE”
• In European Union countries (not Germany) they apply “EN”
• In Russia they often write “starting or starting current”

Autonomous power sources - rechargeable batteries - are seen in modern technologies as an integral element of almost any project. For automotive vehicles, the battery is also a structural part, without which full operation of the vehicle is unthinkable. The universal usefulness of batteries is obvious. But technologically these devices are still not completely perfect. For example, obvious imperfection is indicated by frequent charging of batteries. Of course, the relevant question here is what voltage to charge the battery in order to reduce the frequency of recharging and preserve all its performance properties for a long service life?

Determining the basic battery parameters will help you thoroughly understand the intricacies of the charging/discharging processes of lead-acid batteries (car batteries):

• capacity,
• electrolyte concentration,
• discharge current strength,
• electrolyte temperature,
• self-discharge effect.

The battery capacity receives the electricity given off by each individual battery bank during its discharge. As a rule, the capacity value is expressed in ampere hours (Ah).

On the body of the car battery, not only the rated capacity is indicated, but also the starting current when starting the car when cold. An example of marking - a battery produced by the Tyumen plant

The battery discharge capacity, indicated on the technical label by the manufacturer, is considered a nominal parameter. In addition to this figure, the charge capacity parameter is also significant for operation. The required charge value is calculated by the formula:

Сз = Iз * Тз

where: Iз – charging current; Тз – charging time.

The figure indicating the discharge capacity of the battery is directly related to other technological and design parameters and depends on operating conditions. Among the design and technological properties of the battery, the discharge capacity is influenced by:

• active mass,
• the electrolyte used,
• electrode thickness,
• geometric dimensions of electrodes.

Among the technological parameters, the degree of porosity of the active materials and the recipe for their preparation are also significant for the battery capacity.

The internal structure of a lead-acid car battery, which includes the so-called active materials - plates of negative and positive fields, as well as other components

Operational factors are not left out either. As practice shows, the strength of the discharge current paired with the electrolyte can also influence the battery capacity parameter.

Effect of electrolyte concentration

Excessive electrolyte concentrations will shorten battery life. Operating conditions of a battery with a high concentration of electrolyte lead to an intensification of the reaction, which results in the formation of corrosion on the positive electrode of the battery.

Therefore, it is important to optimize the value, taking into account the conditions in which the battery is used and the requirements set by the manufacturer in relation to such conditions.

Optimizing the concentration of battery electrolyte seems to be one of the important aspects of operating the device. Monitoring the concentration level is mandatory

For example, for conditions with a temperate climate, the recommended level of electrolyte concentration for most car batteries is adjusted to a density of 1.25 - 1.28 g/cm2.

And when the operation of devices in relation to hot climates is relevant, the electrolyte concentration should correspond to a density of 1.22 - 1.24 g/cm2.

Batteries - Discharge Current

The battery discharge process is logically divided into two modes:

1. Long.
2. Short.

The first event is characterized by a discharge at low currents over a relatively long period of time (from 5 to 24 hours).

For the second event (short discharge, starter discharge), on the contrary, large currents are characteristic in a short period of time (seconds, minutes).

An increase in discharge current provokes a decrease in the capacity of the battery.

Teletron charger, which is successfully used to work with lead-acid car batteries. Simple electronic circuit, but high efficiency

Example:

There is a battery with a capacity of 55 A/h with an operating current at the terminals of 2.75 A. Under normal environmental conditions (plus 25-26ºС), the battery capacity is in the range of 55-60 A/h.

If the battery is discharged with a short-term current of 255 A, which is equivalent to increasing the rated capacity by 4.6 times, the rated capacity will drop to 22 A/h. That is, almost double.

Electrolyte temperature and battery self-discharge

The discharge capacity of batteries naturally decreases if the temperature of the electrolyte drops. A drop in the temperature of the electrolyte entails an increase in the degree of viscosity of the liquid component. As a result, the electrical resistance of the active substance increases.

Disconnected from the consumer, completely inactive, it has the ability to lose capacity. This phenomenon is explained by chemical reactions inside the device, which take place even under conditions of complete disconnection from the load.

Both electrodes – negative and positive – are affected by redox reactions. But to a greater extent, the process of self-discharge involves the electrode of negative polarity.

The reaction is accompanied by the formation of hydrogen in gaseous form. With an increase in the concentration of sulfuric acid in the electrolyte solution, there is an increase in the density of the electrolyte from a value of 1.27 g/cm 3 to 1.32 g/cm 3 .

This is commensurate with a 40% increase in the rate of self-discharge effect on the negative electrode. An increase in the self-discharge rate is also provided by metal impurities included in the structure of the negative polarity electrode.

Self-discharge of a car battery after prolonged storage. With complete inactivity and no load, the battery has lost a significant part of its capacity.

It should be noted: any metals present in the electrolyte and other components of batteries enhance the self-discharge effect.

When these metals come into contact with the surface of the negative electrode, they cause a reaction that results in the release of hydrogen.

Some of the existing impurities act as a charge carrier from the positive electrode to the negative electrode. In this case, reactions of reduction and oxidation of metal ions take place (that is, again the process of self-discharge).

There are also cases when the battery loses its charge due to dirt on the case. Due to contamination, a conductive layer is created that short-circuits the positive and negative electrodes

In addition to internal self-discharge, external self-discharge of a car battery cannot be ruled out. The reason for this phenomenon may be a high degree of contamination of the surface of the battery case.

For example, electrolyte, water or other technical liquids have been spilled on the housing. But in this case, the self-discharge effect is easily eliminated. You just need to clean the battery case and keep it clean at all times.

Charging car batteries

Let's start from the situation when the device is inactive (turned off). What voltage or current should I use to charge a car battery when the device is in storage?

Under battery storage conditions, the main purpose of charging is to compensate for self-discharge. In this case, charging is usually performed with low currents.

The range of charge values ​​is usually from 25 to 100 mA. In this case, the charge voltage must be maintained within the range of 2.18 - 2.25 volts in relation to a single battery bank.

Selecting battery charging conditions

The battery charging current is usually adjusted to a certain value depending on the specified charging time.

Preparing a car battery for recharging in a mode that needs to be determined taking into account the technological properties and technical parameters during operation of the battery

So, if you plan to charge the battery for 20 hours, the optimal charge current parameter is considered to be 0.05 C (that is, 5% of the nominal capacity of the battery).

Accordingly, the values ​​will increase proportionally if one of the parameters is changed. For example, with a 10-hour charge, the current will already be 0.1C.

Charging in a two-stage cycle

In this mode, initially (the first stage) a charge is carried out with a current of 1.5 C until the voltage on a separate bank reaches 2.4 volts.

After this, the charger is switched to a charge current mode of 0.1 C and continues to charge until the capacity is full for 2 - 2.5 hours (second stage).

The charge voltage in the second stage mode varies between 2.5 - 2.7 volts for one can.

Forced charge mode

The principle of forced charging involves setting the charging current value at 95% of the nominal battery capacity - 0.95C.

The method is quite aggressive, but it allows you to charge the battery almost completely in just 2.5-3 hours (in practice 90%). Charging up to 100% capacity in a forced mode will take 4 – 5 hours.

Control training cycle

The practice of operating automobile batteries shows a positive result when the control and training cycle is applied to new batteries that have not yet been used.

For this option, charging with parameters calculated by a simple formula is optimal:

I = 0.1 * C20;

Charge until the voltage on a single bank is 2.4 volts, after which the charging current is reduced to the value:

I = 0.05 * C20;

With these parameters, the process is continued until fully charged.

The control and training cycle also covers discharge practice, when the battery is discharged with a small current of 0.1 C to a total voltage level of 10.4 volts.

In this case, the degree of electrolyte density is maintained at 1.24 g/cm 3 . After discharge, the device is charged according to standard methods.

General principles for charging lead-acid batteries

In practice, several methods are used, each of which has its own difficulties and is accompanied by different amounts of financial costs.

Deciding how to charge the battery is not difficult. Another question is what result will be obtained from using this or that method

The most accessible and simplest method is considered to be direct current charging at a voltage of 2.4 - 2.45 volts/cell.

The charging process continues until the current remains constant for 2.5-3 hours. Under these conditions, the battery is considered fully charged.

Meanwhile, the combined charge technique has gained greater recognition among motorists. In this option, the principle of limiting the initial current (0.1 C) until the specified voltage is reached.

The process then continues at a constant voltage (2.4V). For this circuit, it is permissible to increase the initial charge current to 0.3 C, but no more.

It is recommended to charge batteries operating in buffer mode at low voltages. Optimal charge values: 2.23 – 2.27 volts.

Deep discharge - eliminating the consequences

First of all, it should be emphasized: restoring the battery to its nominal capacity is possible, but only under the condition that no more than 2-3 deep discharges have occurred.

The charge in such cases is performed with a constant voltage of 2.45 volts per jar. It is also allowed to charge with a current (constant) of 0.05C.

The battery restoration process may require two or three separate charge cycles. Most often, to achieve full capacity, charging is carried out in 2-3 cycles.

If the charge is carried out with a voltage of 2.25 - 2.27 volts, it is recommended to perform the process twice or three times. Since at low voltages it is not possible to achieve the nominal capacity in most cases.

Of course, the influence of ambient temperature should be taken into account during the restoration process. If the ambient temperature is within the range of 5 – 35ºС, the charging voltage does not need to be changed. Under other conditions, the charge will need to be adjusted.

Video on the control and training cycle of the battery

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