Maximum discharge current. What is battery capacity? Battery voltage

From operating experience

NiMH cells are widely advertised as high-energy, cold-resistant and memoryless. Having bought a Canon PowerShot A 610 digital camera, I naturally equipped it with a capacious memory for 500 high-quality photographs, and to increase the duration of shooting I bought 4 NiMH cells with a capacity of 2500 mAh from Duracell.

Let's compare the characteristics of industrially produced elements:

Options		Lithium ion Li-ion	Nickel-cadmium NiCd	Nickel- metal hydride NiMH	Lead-acid Pb
Duration of service charge/discharge cycles		1-1.5 years	500-1000		3 00-5000
Energy capacity, W*h/kg
Discharge current, mA*battery capacity
Voltage of one element, V
Self-discharge rate		2-5% per month	10% for the first day, 10% for each subsequent month	2 times higher NiCd	40% in year
Permissible temperature range, degrees Celsius	charging
	détente		-20... +65
Permissible voltage range, V		2,5-4,3 (coke), 3,0-4,3 (graphite)			5,25-6,85 (for batteries 6 V), 10,5-13,7 (for batteries 12 V)

Table 1.

From the table we see NiMH elements have a high energy capacity, which makes them preferable when choosing.

To charge them, a DESAY Full-Power Harger smart charger was purchased, which provides charging of NiMH cells with their training. The elements were charged efficiently, but... However, on the sixth charge, it died for a long time. Electronics burned out.

After replacing the charger and several charge-discharge cycles, the batteries began to run out in the second or third ten shots.

It turned out that despite the assurances, NiMH cells also have memory.

And most modern portable devices that use them have built-in protection that turns off the power when a certain minimum voltage is reached. This prevents the battery from being completely discharged. This is where the memory of elements begins to play its role. Cells that are not fully discharged receive an incomplete charge and their capacity decreases with each recharge.

High-quality chargers allow you to charge without losing capacity. But I couldn’t find something like this on sale for elements with a capacity of 2500mAh. All that remains is to periodically train them.

NiMH cell training

Everything written below does not apply to battery cells with strong self-discharge . They can only be thrown away; experience shows that they cannot be trained.

Training NiMH cells consists of several (1-3) discharge-charge cycles.

Discharge is performed until the voltage on the battery cell drops to 1V. It is advisable to discharge the elements individually. The reason is that the ability to accept charge may vary. And it intensifies when charging without training. Therefore, the voltage protection of your device (player, camera, ...) is triggered prematurely and the undischarged element is subsequently charged. The result of this is an increasing loss of capacity.

Discharge must be performed in a special device (Fig. 3), which allows it to be performed individually for each element. If there is no voltage control, then the discharge was carried out until the brightness of the light bulb noticeably decreased.

And if you time the light bulb burning time, you can determine the battery capacity, it is calculated by the formula:

Capacity = Discharge current x Discharge time = I x t (A * hour)

A battery with a capacity of 2500 mAh is capable of delivering a current of 0.75 A to the load for 3.3 hours, if the time obtained as a result of discharging is less, and accordingly the residual capacity is less. And when the required capacity decreases, you need to continue training the battery.

Now, to discharge battery cells, I use a device made according to the circuit shown in Fig. 3.

It is made from an old charger and looks like this:

Only now there are 4 light bulbs, as in Fig. 3. We need to say something about light bulbs separately. If the light bulb has a discharge current equal to the rated current for a given battery or slightly less, it can be used as a load and an indicator, otherwise the light bulb is only an indicator. Then the resistor must be of such a value that the total resistance of El 1-4 and the parallel resistor R 1-4 is about 1.6 Ohms. Replacing a light bulb with an LED is unacceptable.

An example of a light bulb that can be used as a load is a 2.4 V krypton flashlight light bulb.

A special case.

Attention! Manufacturers do not guarantee normal operation of batteries at charging currents exceeding the accelerated charging current. The charge must be less than the battery capacity. So for batteries with a capacity of 2500mAh it should be below 2.5A.

It happens that NiMH cells after discharge have a voltage of less than 1.1 V. In this case, it is necessary to apply the technique described in the above article in the PC WORLD magazine. An element or a series group of elements is connected to a power source through a 21 W car light bulb.

Once again I draw your attention! Such elements must be checked for self-discharge! In most cases, it is the elements with reduced voltage that have increased self-discharge. These items are easier to throw away.

It is preferable to charge individually for each element.

For two elements with a voltage of 1.2 V, the charging voltage should not exceed 5-6V. During forced charging, the light bulb also serves as an indicator. When the brightness of the light bulb decreases, you can check the voltage on the NiMH element. It will be greater than 1.1 V. Typically, this initial, forced charging takes from 1 to 10 minutes.

If the NiMH element does not increase the voltage during forced charging for several minutes and gets hot, this is a reason to remove it from charging and discard it.

I recommend using chargers only with the ability to train (regenerate) the cells when recharging. If there are none, then after 5-6 operating cycles in the equipment, without waiting for a complete loss of capacity, train them and reject elements with strong self-discharge.

And they won't let you down.

One of the forums commented on this article "it's written stupidly, but there's nothing else". So this is not “stupid”, but simple and accessible for anyone who needs help to do in the kitchen. That is, as simple as possible. Advanced people can install a controller, connect a computer, ......, but that’s another story story.

So that it doesn't seem stupid

There are "smart" chargers for NiMH cells.

This charger works with each battery separately.

He can:

1. work individually with each battery in different modes,
2. charge batteries in fast and slow mode,
3. individual LCD display for each battery compartment,
4. charge each battery independently,
5. charge from one to four batteries of different capacities and sizes (AA or AAA),
6. protect the battery from overheating,
7. protect each battery from overcharging,
8. determination of the end of charging by voltage drop,
9. identify faulty batteries,
10. pre-discharge the battery to residual voltage,
11. restore old batteries (charge-discharge training),
12. check battery capacity,
13. display on the LCD display: - charge current, voltage, reflect the current capacity.

The most important thing, I EMPHASIZE, this type of device allows you to work individually with each battery.

According to user reviews, such a charger allows you to restore the majority of neglected batteries, and serviceable ones can be used for the entire guaranteed service life.

Unfortunately, I have not used such a charger, since it is simply impossible to buy it in the provinces, but you can find a lot of reviews in the forums.

The main thing is not to charge at high currents, despite the stated mode with currents of 0.7 - 1A, this is still a small-sized device and can dissipate power of 2-5 W.

Conclusion

Any restoration of NiMh batteries is strictly individual (with each individual element) work. With constant monitoring and rejection of elements that do not accept charging.

And it is best to restore them with the help of intelligent chargers that allow you to individually perform rejection and a charge-discharge cycle with each element. And since there are no such devices that automatically work with batteries of any capacity, they are designed for elements of a strictly defined capacity or must have controlled charging and discharging currents!

This question is periodically asked by customers who buy wheel motors, accessories and batteries for their own conversion of bicycles to electric traction. At first glance, it may seem that there are no current limits in electronic kits and you need to introduce them yourself. Actually this is not true.

Both lead-acid and lithium-ion batteries can briefly withstand maximum currents of up to 10s without destruction - that is, a discharge current that is 10 times their rated capacity. For example, lead-acid batteries with a capacity of 12 amp hours can be loaded with a current of 120 amps for a short time, and lithium-ion batteries with a capacity of 10 amp hours can briefly supply a current of 100 amps.

However, for constant loads these values ​​must be reduced by at least 2 times, that is, to 5s. In Volta bikes lithium batteries, this limitation is implemented in an electronic safety circuit built into the battery. It limits the discharge current to a safe value of 5s, and the voltage to 30 volts. When the load is exceeded or the voltage drops below set limits, the circuit disconnects the battery from the wheel motor, thereby protecting it and ensuring an estimated service life of about 5 years.

Lead-acid batteries do not have such a circuit. Here, the maximum discharge current is limited by the controller itself - to the maximum value specified in its characteristics. When the voltage drops below 10.5 volts (based on one lead-acid battery), Volta bikes controllers also disconnect the batteries from the wheel motor to prevent sulfation and destruction. In addition, the electric bicycle circuit must contain a fuse or circuit breaker, which serves as protection not only from short circuits, but also from overloads. When converting a bicycle to electric power yourself, we recommend installing a 20-amp circuit breaker.

Thus, it will not work to accidentally or even intentionally go beyond the safe operating conditions of lead-acid or lithium Volta bikes batteries. Another question is that a completely discharged battery of any kind should be charged as quickly as possible and, in any case, it is categorically not recommended to leave an electric bike with discharged batteries for the winter somewhere in the garage. Such actions lead to rapid failure of all types of batteries for electric vehicles.

Another misconception is that batteries need to be charged only after a complete discharge - thus, supposedly, the maximum number of charge-discharge cycles specified in the technical specifications is ensured. Think about it: if you do this with the battery of your own car - for example, drive with a faulty generator, and charge the battery at home, after trips, from a charger, then in this mode of operation the starter battery will last at best 2-3 months.

1

And gel lead-acid batteries for electric bikes, and AGM batteries too, differ from starter batteries only in that their electrodes are thicker and they are better fixed in the case to prevent the active mass from shedding. Therefore, they should be recharged as often as possible - after each trip. The same applies to lithium-ion batteries for electric bikes.

As for high discharge currents, it should be remembered that the higher the discharge current, the faster it will completely discharge the batteries of an electric bicycle or electric scooter. Current with a constant load of 1s will discharge high-quality batteries of any type in 1 hour; current 2s - in half an hour, and 4s - in just 15 minutes. Where can you get to with such electricity consumption?

Therefore we recommend:
Firstly, use electricity sparingly if you need to increase the driving distance (please read the article on this topic), secondly, if the batteries run out in less than 50-60 minutes under standard travel modes for you, this is a reason to think about replacing them with more powerful ones.

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 take into account that with an increase in current consumption, 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 ​​for 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 differ 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 service life of a battery usually does not exceed four years, so sooner or later car owners are faced with the question of choosing a new battery for their car. But how do you know what type of battery to choose? What characteristics should you look for? And where can I find their description? We will tell you about this today.

Battery and its types

There are several main types of rechargeable batteries, which differ in the material from which the electrodes are made and the composition of the electrolyte. Many of you know that there are various nickel-cadmium, nickel-metal hydride, lithium-ion, and lead-acid batteries. From this list, only one is used as a starter - lead. This is due to the fact that this type of battery is endowed with the largest possible reserve of electrical capacity, in comparison with others, and is capable of instantly delivering high current.

But with all this, you have to put up with the fact that their filling is very harmful, because it contains lead and acid. To ensure maximum operating safety for lead-acid batteries, their cases are made of special acid-resistant plastic. Today, the material from which electrodes are made is lead, not in its pure form, of course, but with various additives, on which the further division of batteries into several types depends:

- Traditional, which is also called antimony;

Low antimony;

Calcium;

Hybrid;

Gel or AGM;

Alkaline;

Traditional or antimony

Rechargeable batteries of this type also contain lead electrodes. 5% antimony They are also called simply classic or traditional. But today the relevance of these names no longer has a direct meaning, because the antimony content has decreased significantly. Antimony is added to the alloy in the electrodes to increase their strength. But this additive also speeds up the electrolysis process, which begins already at around 12 volts. A large amount of gases are released and a feeling of boiling water occurs. Due to the evaporation of water in large volumes, the electrolyte changes its concentration to a stronger one, causing the top of the electrodes to become exposed. In order to restore the water balance of the electrolyte, distilled water is added to it.

Batteries with a high content of antimony additives are very easy to maintain. This is due to the fact that you need to check the electrolyte concentration monthly and add distilled water if necessary. Such batteries are no longer installed in new car models, because progress is rapidly moving forward. These batteries are still installed in fixed installations, where unpretentiousness is important and there are no problems with servicing power supplies. Car batteries are now manufactured without the addition of antimony or their amount is minimized to the maximum.

Low antimony

To avoid strong evaporation of water from the electrolyte, battery plates, as mentioned above, began to be made with minimal antimony additives, the amount of which does not reach 5%. As a result, the frequent need to check the electrolyte concentration level has fallen into oblivion. Self-discharge during long-term storage of the battery has also decreased.

This type of battery is one that requires little or no maintenance. This is justified by the fact that the insides of the battery do not require monitoring or maintenance. Although, in essence, such a term as “maintenance-free” refers to an unrealized theory or, most likely, to cunning marketing operations, because they have not yet reached the level at which the water from the electrolyte does not boil away at all. It gradually evaporates anyway, although in much smaller volumes than those of those batteries that are called serviceable.

Calcium

Manufacturers are still struggling with how to make a completely maintenance-free battery so that the water in it does not evaporate at all. To do this, the antimony in the electrode plate grids was replaced with another, more suitable material. This turned out to be calcium. Calcium batteries are often marked with the letters “Ca/Ca”. This designation tells car owners that the plates of both poles contain calcium.

In addition, silver is sometimes added to the electrodes in very small quantities. This reduces the resistance inside the battery, which has a good effect on its performance and energy capacity. The calcium in the lead plates did an excellent job of reducing gas emissions and water loss, which puts this type an order of magnitude higher than low-antimony batteries. The loss of water during battery operation is so negligible that the need to check the electrolyte concentration and its level in the banks has simply become unnecessary.

Thus, calcium-type batteries can rightfully be called maintenance-free. In addition to less water loss, calcium batteries also have a 70% lower self-discharge level compared to previous opponents. This allows these batteries to maintain their performance for a longer period. Such batteries are installed in factories producing foreign cars in the mid-price segment, where the manufacturer boldly guarantees the stability and quality of electrical equipment.

But when buying a battery of this type, know that it requires more careful care than a low-antimony one. But with proper maintenance, you will have a reliable and stable high-quality power source.

Hybrid

The type of these batteries is marked as “Ca+”. Hybrid batteries have electrode plates that are created using different technologies: the positive electrodes are low-antimony, and the negative electrodes are calcium. This technology made it possible to combine the positive aspects of both types in one battery. Water in hybrid batteries is consumed 50% slower than in low-antimony batteries, but still faster than in calcium batteries. But hybrids are much more resistant to overcharging. According to their characteristics, they rightfully occupy a niche between the two previous representatives.

Gel or AGM

Banks of gel batteries are filled with electrolyte not in a liquid state we understand, but in a gel-like, fixed state, which is where the name of this type comes from. Thanks to this state of the electrolyte, these batteries are not afraid of tilting, because the gel is not as liquid as liquid. Although this is again a professional “tempting” marketing ploy, and it’s better not to turn over gel-filled batteries. Although manufacturers write that such batteries can be used in any convenient position.

The positive aspects of AGM batteries do not end with excellent vibration resistance. They also self-discharge slowly, thanks to which they can withstand long-term storage without fear of a critical decrease in charge. They should be stored in a fully charged state.

The current supplied by the battery, depending on the charge, remains unchanged even until it is completely discharged. They are also not afraid of overdischarge; they completely restore their previous capacity even after recharging. But the situation with charging gel-type batteries is not as smooth as with discharging. Such batteries cannot be rapidly charged. They should be charged with a very low current. For this purpose, even chargers are produced that are specially adapted for charging gel batteries.

Although the market is rich in universal chargers, which are supposed to charge any type of battery. How much of this is really true cannot be answered unequivocally, because there are different manufacturers and it is better to pay attention to those that are already established in the market and have proven themselves well.

The negative side of gel batteries is their “fear” of extremely low temperatures. The lower the ambient temperature, the lower the conductivity of the gel electrolyte becomes. If operating conditions are favorable, such batteries can last for ten years.

Alkaline

Did you know that the electrolyte in batteries can have not only an acidic, but also an alkaline component? And there are many varieties of such batteries, but we will take for review only those that are used in cars.

But car alkaline batteries come in only two types: nickel-cadmium And nickel-iron. The first type of battery has positive electrodes coated with nickel hydroxide NiO(OH), and negative electrodes coated with iron mixed with cadmium. In the second type of battery, the positive electrodes are coated identically to those in a nickel-cadmium battery, that is, nickel hydroxide. But in the negative electrode there are already differences; here it is made of pure, without impurities, iron. The alkaline electrolyte in both types of batteries is a solution of caustic potassium.

This and the last type of battery on our list is considered the most promising today. The electrolyte of this type of battery contains lithium ions. It is impossible to say for sure what material the electrode plates are made of, because manufacturing technology is constantly moving forward. However, we know that they were originally produced by lithium metal, but due to their explosiveness, such electrodes were no longer used. They were replaced by graphite plates. For positively charged electrodes, lithium oxide with the addition of cobalt or manganese was used. But at the present time they are being replaced by lithium ferrophosphate, because the new material is much less toxic, more accessible and environmentally friendly. Such plates can be safely disposed of.

Work is constantly underway to improve existing types of batteries, and it is continuous. Research and testing centers are working tirelessly to find more energy-intensive power supplies in compact sizes. For regions with extreme winters, the invention of batteries resistant to severe frost would be useful, then the problem with motor failure would be solved. The movement towards environmental friendliness is also important. After all, today we have not yet learned how to produce completely environmentally friendly batteries.

It is not yet possible to do without adding toxic elements, such as, for example, lead, alkali, sulfuric acid. But for traditional batteries, the future is most likely closed. An intermediate evolutionary stage is gel batteries. The battery of the future is seen without filling with liquid, of arbitrary shape, as well as with many other parameters that will relieve car owners from worrying about whether the electrolyte has spilled out or whether the battery will fail. The driver should enjoy the trip.

Technical characteristics: weight, current, capacity, voltage

The most important indicators of battery quality are: voltage, weight, capacity, dimensions, nominal depth of discharge, service life, efficiency, operating temperature range, permissible charge and discharge current. Also take into account the fact that the characteristics specified by the manufacturer are valid for temperatures of 20-25 degrees Celsius. If you deviate from these numbers, they change and often not for the better.

Voltage and capacity values ​​are often used in the name of the battery model. For example, the RA12200DG battery. The battery voltage is 12 Volts, its capacity is 200 Ah, gel electrolyte, deep-discharge. This battery produces energy of 2.4 kW, based on the formula 12 x 200 = 2400 Wh when discharged with current for ten hours at 10% of the total capacity. With deviations towards higher current and rapid discharge, the capacity of such a battery decreases. At lower currents, on the contrary, it often increases. You need to look at the discharge characteristics of certain batteries that interest you. Sometimes manufacturers indicate in the name an overly ideal battery capacity, which is only possible in utopian conditions. Such fans, for example, Haze, whose capacity in reality is an order of magnitude lower than declared, namely by 10-20 points, and this is significant, you will agree.

Battery capacity

The amount of energy that a battery can store is called its capacity. It is measured in ampere hours A/h. For example, one battery with a capacity of 100 ampere hours can supply a current of 1 amp for 100 hours, or a current of 5 amps for 20 hours, and so on. Although the battery capacity decreases if the discharge current increases. On the market you can purchase batteries with capacities from 1 to 2000 A/h.

Life time

To extend the life of a lead-acid battery, it is best to use only a small portion of its capacity before recharging. Each process that is accompanied by discharging and recharging the battery is called a charging cycle, and it is not necessary to completely discharge the battery. Let's say you discharged the battery by a quarter, and then charged it again, then it has one charging cycle. But the number of cycles will directly depend on the depth of discharge.

If a battery can be discharged to more than half its rated capacity without significantly degrading its parameters, then such a unit is called “deep-discharge”. The battery may be damaged if it is overcharged more than necessary. The maximum voltage supplied to a 12-volt acid battery should not exceed 15 watts. A significant part of photovoltaic batteries have a soft load characteristic, so as the voltage increases, the charging current decreases significantly. Let's say that for solar panels you always need to use a certain charge controller. Its use is also necessary for wind power plants and microhydroelectric power plants.

Voltage

Battery voltage is often the main parameter by monitoring which you can determine how charged the battery is and in what condition it is. This is especially true for batteries in a sealed shell, in which it is physically impossible to measure the electrolyte concentration without damaging them. In order to determine how much, its voltage is measured at the terminals for 4-5 hours in the absence of charging and discharging currents.

The voltage measured while charging or discharging the battery will not tell you anything about how charged the battery is. The dependence of how charged the battery is on the voltage on it in idle mode is different for different types of batteries. For batteries that are sealed, for example, gel batteries are slightly larger than those types that have liquid electrolyte. For example, an AGM battery is considered fully charged if its voltage is 13 watts, while for acid batteries it is 12.5 watts.

Charge level

The extent to which a battery is charged depends on many factors. And only special devices with memory and a microprocessor can accurately determine the battery charge. They monitor the charge and discharge of the battery over several charging cycles. Using this method will give you the most accurate readings about the charge of the battery, but it will also take a considerable amount of money. But you shouldn’t skimp on using this method, because you can avoid unnecessary expenses during further maintenance and replacement of the battery. By using special devices that control the operation of batteries based on their degree of charge, you will significantly increase the service life of your lead-acid battery.

To determine how charged the battery of your car is, the following two methods, which are simplified, are successfully used.

Battery voltage

This method is not very accurate, but to use it you only need a digital voltmeter with sensitivity up to a hundredth of a volt. Before starting measurements, it will be necessary to disconnect the battery from all electrical consumers that discharge it and from devices that charge it. Wait at least two hours and start measuring at the battery terminals. A 100% charged gel battery will have a voltage of 13 watt against 12.5 watts for liquid electrolyte batteries. As a battery begins to age, its voltage decreases. The voltage can be measured both on the entire battery and on each bank. To find a faulty one, for example in a 12-volt battery, you need to divide the total voltage by the number of cells, in this case 6.

Electrolyte density

The next method for checking battery charge is by electrolyte density. As has already become clear, it is only suitable for batteries with liquid filler; a priori, it cannot be used for gel batteries, for example. Also, as in the first method, you need to wait at least two hours before starting measurements. Measurements are made with a hydrometer. Important! Before starting the procedure, be sure to protect yourself by wearing gloves and plastic safety glasses. Keep baking soda and water on hand in case the electrolyte gets on your skin.

Battery life

It is not entirely correct to define the service life in terms of time periods. Battery life is calculated by charging cycles and depends directly on operating conditions. The greater the depth of discharge of the battery and the longer it is in a discharged state, the more significantly the number of its operating cycles is reduced.

As we have already understood, the concept of the number of charging cycles is absolutely relative, because it directly depends on many factors. In addition, the number of life cycles of one battery will not be the same for another; this concept is not universal. After all, everything again depends on operating factors and production technology, which differs from one manufacturer to another. Remember that the battery life is calculated by charging cycles, and the time intervals are approximately calculated in cases where the battery is used continuously under typical conditions.

Another important point is that the useful capacity of the battery decreases as the battery is used. All characteristics based on the number of cycles are determined not until the battery is completely exhausted, but until it loses 40; from its nominal capacity. For example, if the manufacturer specified a number of 600 cycles with a charge equal to half its capacity, this means that after 600 identical cycles under ideal conditions, the useful capacity of the battery will be 60% of the factory capacity. And even with this capacity value, manufacturers recommend replacing the battery. Lead-acid batteries have a service life ranging from 300 to 3000 cycles, depending on the type and depth of discharge of the battery.

To ensure long service life, the battery discharge in a typical cycle should not exceed 30% , and deep discharge – 80% containers. If the lead-acid battery is discharged, it needs to be charged as quickly as possible. If such a battery has been in a completely discharged or undercharged state for more than 12 hours, then the consequences of what happened to it may be irreversible and its service life will sharply decrease.

How can you tell if your battery is nearing its limit? Everything is very simple. The internal resistance of the battery increases sharply, which leads to a voltage surge during charging, as a result of which the charging period itself decreases and the battery discharges more quickly. If you start charging a dying battery with a current that is close to the limit, it will get very hot, much hotter than before.

Maximum charge and discharge currents

The charge and discharge currents of any battery are measured depending on its capacity. As a rule, the maximum charging current for a battery should not exceed more than 0.3C. Exceeding the charging current will lead to a reduction in the service life of the battery. We recommend setting the charging current to no more than 0.2C.

Self-discharge

Self-discharge, as a phenomenon, is characteristic of all types of batteries to a lesser or greater extent and consists in the loss of their capacitive characteristics after they have been fully charged in the absence of an external energy consumer. In order to conveniently quantify the self-discharge of a battery, it will be convenient to use the amount of lost capacity over a certain period of time, which is expressed as a percentage of the value obtained immediately after a full charge. As a rule, an interval is taken as a time period, which is equal to one day or one month.

For example, if you take a working NiCD battery, then the permissible self-discharge is 10% per day after charging is complete. For NiMH batteries - a little more, but for Li-ION it is completely small and is estimated in a month. In lead batteries, self-discharge is already calculated in years, because it is much reduced and amounts to 40% per year at a temperature of 20 degrees Celsius and 15% at a temperature of 5 degrees. If the storage temperature is much higher, then self-discharge occurs faster.

For example, at a temperature of 40 degrees, the battery will lose its 40% capacity in just 5 months. Note that the battery self-discharges strongly only in the first day after charging, and after that it subsides significantly. If the battery is subjected to deep discharge and subsequent charging, this aggravates its self-discharge. The self-discharge process gains strength at elevated temperatures. So, for example, if the ambient temperature rises sharply by 10 degrees relative to the usual one, then the self-discharge will double.

The container can also be wasted if the separator is damaged, when the crystals stick together, forming a large lump that pierces it. The separator in a battery is a thin plate that separates the electrodes with positive and negative charges. This happens when the battery is improperly maintained or not maintained at all. This can also happen if you use low-quality charging devices or those that do not meet the necessary parameters. If the battery is worn out, its electrode plates stick to each other due to their swelling. This leads to accelerated self-discharge. At this stage, the damaged separator can no longer be restored by charging/discharging.

Marking - we find out the charge capacity, current strength and other parameters

exists so that you, as a buyer, can obtain detailed necessary information about all the necessary technical characteristics of the battery you are interested in. It includes: battery type, trademark and production date, weight and compliance with GOST. The number of batteries combined into a single battery is also indicated; as a rule, there should be 3 or 6. The letters “St” tell you that you are looking at an old battery in front of you. Depending on the material used to make the monoblock body, the corresponding letter is indicated:

E– ebonite;

P– asphalt pitch plastic;

T– thermoplastic.

The material from which the separators are made is also important. If the marking contains a capital letter "R", then this is a mipora, a letter "M" points to the miplast, and "WITH"- it's fiberglass.

The voltage, as such, is not indicated on the battery label; it is simply not necessary, because it is a standard value that can be measured with a regular load plug. Also pay attention to the presence of the letter “Z”, if there is one. If present, this indicates a flooded battery that is fully charged. If this letter is missing, then the battery is dry-charged.

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 charging technique has gained greater recognition among motorists. In this option, the principle of limiting the initial current (0.1C) 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 charge 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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