Designing a charger for lead acid battery. Types of Lead Acid Batteries

New developments in the field of battery manufacturing, after carrying out the necessary tests, are immediately introduced into production. This is due to the fact that the battery is a consumable part of the car. The internal elements of the battery operate in an aggressive environment, while vibration and a wide range of operating temperatures have a destructive effect on thin plates and separators.

Contents

What are VRLA batteries

In the past, constant evaporation of water led to exposure of the metal parts of the electrodes and even more intense destruction of the lead elements. To reduce the negative impact of destructive factors, modern batteries are made, that is, opening the lid and adding distilled water in such products will no longer work. The most advanced in this regard is AGM VRLA technology.

VRLA technology stands for Valve Regulated Lead Acid, which means an acid battery with a special control valve. Such batteries are produced in a completely closed case, but due to the presence of a safety system, if high internal pressure occurs, the battery does not collapse.

Despite the connection with the atmosphere through the valve hole, such a battery does not require maintenance, because evaporation of liquid occurs in exceptional cases. For example, during daily use such a locking mechanism remains closed, but if you forget to turn on the charger for a long period of time, then a very small part of the water from the electrolyte can escape through the automatically opened hole.

Features of the technology

Batteries with a safety valve can be manufactured using various technologies.

AGM VRLA Battery

VRLA AGM are sealed valve batteries with plates manufactured to . Such products have a long shelf life thanks to the absorbent fiberglass layer, which absorbs all the electrolyte and at the same time supports the lead plates, protecting them from shedding.

VRLA GEL

This, that is, inside the jar, instead of a liquid solution of sulfuric acid, there is a jelly-like substance that acts as an electrolyte. VRLA Batteries made using gel technology are also equipped with a valve.

Due to the fact that the gel has a less destructive effect on the plates, and when excess pressure occurs in such a battery, the safety device opens, the service life of the product can reach 10 years.

Given the presence of such important qualities as high reliability, resistance to deep discharge and long shelf life, VRLA batteries have become widespread in many areas of economic activity where a reliable chemical source of electricity is required.

Where are VRLA batteries used?

This battery production technology is most widely used in mechanical engineering. The presence of a valve that opens only when excess pressure occurs has made it possible to abandon the outdated type of housing, which is a design equipped with screw-in plugs. The inability of the driver to open access to the banks significantly increased the shelf life of the product.

VRLA batteries are resistant to deep discharges, so they can be used not only as starter batteries, but also to equip uninterruptible power supply devices. For the same reason, such battery models are used as the main energy accumulator for boats equipped with an electric motor, golf carts and wheelchairs.

How to charge VRLA batteries

Charging a VRLA battery depends on the technology used to manufacture the battery. If a product of this type has an electrolyte in the form of a gel, then, despite the presence of a safety valve, it is necessary to ensure that gas formation inside the product does not become too active.

In the case when the capacity of such a battery is restored by applying a voltage of more than 15 Volts, not only will the volume of the electrolyte decrease, but also the jelly-like mass will separate from the plates, which will lead to an inevitable decrease in the capacity of the battery and its death. To reduce the likelihood of failure of this type of battery when charging, it is recommended to use special chargers that supply electric current to the terminals automatically, adjusting the current and voltage depending on the charge of the battery and its temperature.

VRLA batteries made using AGM technology are more resistant to charging errors, but in order to maximize the service life of such a battery, it is not recommended to exceed the following indicators:

• Charge voltage - 14.8 V.
• Charging current – ​​10% of battery capacity.

When restoring the battery's functionality in this way, the duration of connection to the charger should be about 10 hours.

As with charging gel products, AGM batteries equipped with a safety valve can be restored using automatic chargers. Such devices will require minimal human supervision.

You had or have a Battery VRLA? Then tell us in the comments about your impressions of it, this will greatly help other car enthusiasts and make the material more complete and accurate.

Types of Lead Acid Batteries

Currently, the most common types of batteries on the battery market are:

- SLA (Sealed Lead Acid) Sealed lead acid or VRLA (Valve Regulated Lead Acid) valve-regulated lead acid. Manufactured using standard technology. Due to the design and materials used, there is no need to check the electrolyte level or add water. They have low cycling resistance, limited low-discharge capabilities, standard inrush current and fast discharge.

- EFB (Enhanced Flooded Battery) The technology was developed by Bosch. This is an intermediate technology between standard and AGM technologies. Such batteries are distinguished from standard ones by higher cycling resistance and improved charge acceptance. They have a higher starting current. Like SLA\VRLA, there are limitations to operating at low levels of charge.

- AGM (Absorbed Glass Mat) Currently the best technology (in terms of price/performance ratio). Cycling resistance is 3-4 times higher, fast charging. Due to its low internal resistance, it has a high inrush current at a low state of charge. Water consumption is close to zero, resistant to electrolyte separation due to absorption in the AGM separator.

- GEL (Gel Electrolite) A technology in which the electrolyte is in the form of a gel. Compared to AGM, they have better cycling resistance and greater resistance to electrolyte separation. The disadvantages include high cost and high requirements for charging mode.

There are several other battery manufacturing technologies, both related to changes in the shape of the plates and specific operating conditions. Despite the difference in technology, the physical and chemical processes that occur during battery charging and discharging are the same. Therefore, the charging algorithms for different types of batteries are almost identical. The differences are mainly related to the value of the maximum charge current and the end of charge voltage.

For example, when charging a 12-volt battery using technology:

Determining the state of charge of the battery

There are two main ways to determine the state of charge of a battery, measuring the density of the electrolyte and measuring the open circuit voltage (OCV).

NRC is the voltage on the battery without a connected load. For sealed (maintenance-free) batteries, the degree of charge can only be determined by measuring the NRC. It is necessary to measure the NRC no earlier than 8 hours after stopping the engine (disconnecting from the charger), using a voltmeter with an accuracy class of at least 1.0. At a battery temperature of 20-25°C (according to Bosch recommendations). The NRP values ​​are given in the table.

(for some manufacturers, the values ​​may differ from those shown) If the battery charge level is less than 80%, it is recommended to charge it.

Battery charging algorithms

There are several most common battery charging algorithms. Currently, most battery manufacturers recommend the CC\CV (Constant Current\Constant Voltage) charging algorithm.

This algorithm provides a fairly fast and “gentle” battery charging mode. To prevent the battery from remaining for a long time at the end of the charging process, most chargers switch to the mode of maintaining (compensating for self-discharge current) the voltage on the battery. This algorithm is called three-stage. The graph of such a charging algorithm is shown in the figure.

The indicated voltage values ​​(14.5V and 13.2V) are valid when charging batteries of the SLA\VRLA,AGM type. When charging GEL type batteries, the voltage values ​​should be set to 14.1V and 13.2V, respectively.

Additional algorithms for charging batteries

Precharge A heavily discharged battery (NRC less than 10V) has an increase in internal resistance, which leads to a deterioration in its ability to accept a charge. The precharge algorithm is designed to “boost” such batteries.

Asymmetric charge To reduce sulfation of the battery plates, you can charge with an asymmetric current. With this algorithm, charge alternates with discharge, which leads to partial dissolution of sulfates and restoration of battery capacity.

Equalizing charge During the operation of batteries, the internal resistance of individual “cans” changes, which leads to uneven charge during charging. To reduce the spread of internal resistance, it is recommended to carry out an equalizing charge. In this case, the battery is charged with a current of 0.05...0.1C at a voltage of 15.6...16.4V. The charge is carried out for 2...6 hours with constant monitoring of the battery temperature. You cannot equalize charge sealed batteries, especially using GEL technology. Some manufacturers allow such a charge for VRLA\AGM batteries.

Determining battery capacity

As the battery is used, its capacity decreases. If the capacity is 80% of the nominal, then it is recommended to replace the battery. To determine the capacity, the battery is fully charged. Allow to stand for 1....5 hours and then discharge with a current of 1\20C to a voltage of 10.8V (for a 12-volt battery). The number of ampere hours supplied by the battery is its actual capacity. Some manufacturers use other values ​​of discharge current and voltage to which the battery is discharged to determine capacity.

Control training cycle

To reduce sulfation of battery plates, one of the methods is to conduct control training cycles (CTC). CTCs consist of several successive charge cycles followed by discharge with a current of 0.01...0.05C. When carrying out such cycles, the sulfate dissolves and the battery capacity can be partially restored.

We need reliable information on this topic.

Here's what I found on the Internet:
Batteries:
Sealed lead-acid batteries.
In the international interpretation, the designation is accepted in the form of SEALED LEAD ACID BATTERY or SLA for short.
The lead-acid battery, invented in 1859, was the first rechargeable battery designed for commercial use. Today, flooded lead-acid batteries are used in vehicles and equipment that require high power output. Portable devices use sealed batteries or batteries with a regulating valve that opens when the pressure inside the housing increases above a preset threshold.
There are several technologies for manufacturing SLA batteries: Gelled Electrolite (GEL), Absorptive Glass Mat (AGM), as well as various hybrid technologies that use one or more ways to improve battery parameters. When manufactured using GEL technology, by adding special substances to the electrolyte, it is ensured that it transforms into a jelly-like state several hours after the battery is filled. In the thickness of the jelly-like electrolyte, the formation of pores and shells occurs, having a significant volume and surface area, where oxygen and hydrogen molecules meet and recombine to form water. As a result, the amount of electrolyte remains unchanged and adding water is not required throughout the entire service life. AGM technology uses a porous fiberglass core impregnated with liquid electrolyte. The micropores of this material are not completely filled with electrolyte. The free volume is used for gas recombination.
SLA batteries are usually used in cases where high power output is required, weight is not critical, and cost should be minimal. The range of capacity values ​​for portable devices is from 1 to 30 A*hour. Large SLA batteries for stationary applications have capacities from 50 to 200 A*h.
SLA batteries are not subject to the "memory effect". It is possible to leave the battery in the charger on a floating charge for a long time without any harm. Charge retention is the best among rechargeable batteries. Whereas NiCd batteries self-discharge by 40% of stored energy in three months, SLA batteries self-discharge by the same amount in one year. These batteries are inexpensive, but their operating costs can be higher than NiCd batteries if they require a large number of charge/discharge cycles over their lifespan.
Fast charging mode is unacceptable for SLA batteries. Typical charging time is from 8 to 16 hours.
Unlike NiCd, SLA batteries do not like deep discharge cycles and storage in a discharged state. This causes the battery plates to sulfate, making them difficult, if not impossible, to charge. In fact, each charge/discharge cycle removes a small amount of capacity from the battery. This loss is very small if the battery is in good condition, but becomes more noticeable as soon as the capacity drops below 80% of the rated capacity. This is also true to varying degrees for batteries of other electrochemical systems. To reduce the impact of deep discharge, you can use a slightly larger SLA battery.
Depending on the depth of discharge and operating temperature, the SLA battery provides from 200 to 500 charge/discharge cycles. The main reason for the relatively low number of cycles is the expansion of the positive plates as a result of internal chemical reactions. This phenomenon is most pronounced at higher temperatures. SLA batteries have a relatively low energy density compared to other batteries and are therefore unsuitable for compact devices. This becomes especially critical at low temperatures, since the ability to deliver current to the load at low temperatures is significantly reduced. Paradoxically, the SLA battery charges very well with alternating discharge pulses. During these pulses, the discharge current can reach values ​​greater than 1C (rated capacity).
Due to their high lead content, SLA batteries are environmentally harmful if not disposed of correctly.
Nickel-cadmium batteries.
In the international interpretation, the designation NICKEL-CADMIUM BATTERY or NiCd for short is accepted.
Alkaline nickel battery technology was first proposed in 1899. The materials used in them were expensive at that time and batteries were used only in the manufacture of special equipment. In 1932, active substances were added to a porous nickel plate electrode, and in 1947, research began on sealed NiCd batteries, in which internal gases released during charging were recombined internally, rather than released outside as in previous versions. These improvements led to the modern sealed NiCd battery used today.
The NiCd battery is a veteran in the mobile and portable device market. Its proven technology and reliable performance have made it widely used to power portable radios, medical equipment, professional video cameras, recording devices, heavy-duty hand tools and other portable equipment. The emergence of batteries of newer electrochemical systems, although it has led to a decrease in the use of NiCd batteries, however, the identification of the shortcomings of new types of batteries has led to renewed interest in NiCd batteries.
Their main advantages:
fast and easy charging method;
long service life - over a thousand charge/discharge cycles, subject to the rules of operation and maintenance;
excellent load capacity, even at low temperatures. The NiCd battery can be recharged at low temperatures;
easy storage and transportation. NiCd batteries are accepted by most air cargo companies;
easy recovery after capacity reduction and long-term storage;
low sensitivity to incorrect consumer actions;
affordable price;
wide range of standard sizes.
The NiCd battery is like a strong and silent worker who works intensively without causing much trouble. It prefers a fast charge over a slow charge and a pulse charge over a direct current charge. Improved efficiency is achieved by distributing discharge pulses between charge pulses. This charging method, commonly called reverse charging, restores the structure of the cadmium anodes, thereby eliminating the "memory effect", and increases the efficiency and life of the battery. In addition, reverse charging allows you to charge with a higher current in less time, because helps recombine gases released during charging. As a result, the battery runs cooler and charges more efficiently compared to standard DC charging methods. Research conducted in Germany showed that reverse charging adds about 15% to the service life of a NiCd battery.
It is harmful for NiCd batteries to remain in a charger for several days. In fact, NiCd batteries are the only type of battery that performs best if subjected to a full discharge periodically, and if not, the batteries gradually lose efficiency due to the formation of large crystals on the cell plates, a phenomenon called the "memory effect" ". For all other types of batteries using the electrochemical system, a shallow discharge is preferable.
Among the disadvantages of the NiCd battery, the following should be noted:
the presence of a “memory effect” and, as a result, the need for complete periodic discharge to maintain operational properties;
high self-discharge (up to 10% during the first 24 hours), so batteries must be stored in a discharged state;
The battery contains cadmium and requires special disposal. In a number of countries, for this reason, it is currently prohibited for use.
Nickel-metal hydride batteries. In the international interpretation, the designation is NICKEL METAL-HYDRIDE BATTERY or NiMH for short.
Research into NiMH battery technology began in the seventies to overcome the shortcomings of nickel-cadmium batteries. However, the metal hydride compounds used at that time were unstable and the required characteristics were not achieved. As a result, developments in the NiMH battery field have slowed. New metal hydride compounds stable enough for battery use were developed in 1980. Since the late eighties, the manufacturing technology of NiMH batteries has been constantly improved, and the energy density they store has increased.
Some distinctive advantages of today's NiMH batteries:
approximately 40 - 50% higher specific capacity compared to standard NiCd batteries;
less prone to "memory effect" than NiCd. Periodic recovery cycles should be performed less frequently;
less toxicity. NiMH technology is considered environmentally friendly.
Unfortunately, NiMH batteries have disadvantages and are inferior to NiCd in some respects:
The number of charge/discharge cycles for NiMH batteries is approximately 500. Shallow rather than deep discharge is preferred. The durability of batteries is directly related to the depth of discharge;
A NiMH battery generates significantly more heat during charging than a NiCd battery and requires a more complex algorithm to detect when it is fully charged unless temperature control is used. Most NiMH batteries are equipped with an internal temperature sensor to provide additional criteria for fully charged detection. A NiMH battery cannot charge as quickly as a NiCd; charging time is typically twice that of NiCd. The float charge must be more controlled than for NiCd batteries;
The recommended discharge current for NiMH batteries is from 0.2C to 0.5C - significantly less than for NiCd. This disadvantage is not critical if the required load current is low. For applications that require high load current or have a pulse load, such as portable radios and heavy-duty hand tools, NiCd batteries are recommended;
self-discharge of NiMH batteries is 1.5-2 times higher than that of NiCd;
the price of NiMH batteries is approximately 30% higher than NiCd. However, this is not a major problem if the user requires large capacity and small dimensions.
The manufacturing technology of nickel-metal hydride batteries is constantly being improved. For example, GP Batteries International Limited manufactures NiMH batteries for Motorola cell phones with the following characteristics: number of charge/discharge cycles - 1000, no “memory effect” and no need to discharge the battery before charging.
Lithium-ion batteries. In the international interpretation, the designation is accepted as LITHIUM ION BATTERY or Li-ion for short.
Lithium is the lightest metal and has a strongly negative electrochemical potential. Due to this, lithium is characterized by the highest theoretical specific electrical energy.
The first work on lithium batteries dates back to 1912. However, it was only in 1970 that commercial copies of lithium power sources were first produced. Attempts to develop rechargeable lithium power sources were made in the 80s, but were unsuccessful due to the impossibility of ensuring an acceptable level of safety during their operation.
As a result of research carried out in the 80s, it was found that during cycling of a current source with a lithium metal electrode, a short circuit could occur within the lithium current source. In this case, the temperature inside the battery can reach the melting point of lithium. As a result of the violent chemical interaction of lithium with the electrolyte, an explosion occurs. Therefore, for example, a large number of lithium batteries supplied to Japan in 1991 were returned to the manufacturers after several people suffered burns as a result of cell phone battery explosions.
In the process of creating a safe lithium-based power source, research has led to the replacement of cycling-unstable lithium metal in the battery with its compounds with other substances. These electrode materials have several times lower specific electrical energy compared to lithium, however, batteries based on them are quite safe, provided that certain precautions are taken during charging/discharging. In 1991, Sony began commercial production of lithium-ion batteries and is currently one of the largest suppliers.
To ensure safety and longevity, each battery must be equipped with an electrical control circuitry to limit the peak voltage of each cell during charging and prevent cell voltage from dropping below an acceptable level when discharged. In addition, the maximum charge and discharge current must be limited and the cell temperature must be monitored. If these precautions are observed, the possibility of the formation of lithium metal on the surface of the electrodes during operation (which most often leads to undesirable consequences) is practically eliminated.
Based on the negative electrode material, lithium-ion batteries can be divided into two main types: coke-based negative electrode (Sony) and graphite-based (most other manufacturers). Current sources with a graphite-based negative electrode have a smoother discharge curve with a sharp voltage drop at the end of the discharge, compared to the flatter discharge curve of a battery with a coke electrode. Therefore, in order to obtain the highest possible capacity, the final discharge voltage of batteries with a negative coke electrode is usually set lower (up to 2.5 V) compared to batteries with a graphite electrode (up to 3.0 V). In addition, batteries with a negative graphite electrode are capable of delivering higher load current and less heat during charge and discharge than batteries with a negative coke electrode. The 3.0 V end-of-discharge voltage for batteries with a negative graphite electrode is its main advantage, since the useful energy in this case is concentrated within a tight upper voltage range, thereby simplifying the design of portable devices.
Manufacturers are continuously improving Li-ion battery technology. There is a constant search and improvement of electrode materials and electrolyte composition. In parallel, measures are being taken to improve the safety of Li-ion batteries, both at the level of individual current sources and at the level of control electrical circuits. Since these batteries have a very high specific energy, care must be taken when handling and testing them: do not short-circuit the battery, overcharge, destroy, disassemble, connect in reverse polarity, and do not expose them to high temperatures. Violation of these rules may result in physical and property damage.
Lithium-ion batteries are the most promising batteries at present and are beginning to be widely used in laptop computers and mobile communication devices. This is due to:
high electrical energy density, at least twice that of NiCd of the same size, and therefore half the size with the same capacity;
a large number of charge/discharge cycles (from 500 to 1000);
good performance at high load currents, which is necessary, for example, when using these batteries in cell phones and laptop computers;
fairly low self-discharge (2-5% per month plus about 3% for powering the built-in electronic protection circuit);
absence of any maintenance requirements, except for the need for pre-charging before long-term storage;
allow charging at any degree of battery discharge.

But here, too, there is a “fly in the ointment”: for batteries from some manufacturers, they are guaranteed to operate only at positive temperatures, have a high price (about twice the price of NiCd batteries) and are susceptible to the aging process, even if the battery is not used. Deterioration in parameters is observed after approximately one year from the date of manufacture. After two years of service, the battery often becomes faulty. Therefore, it is not recommended to store Li-ion batteries for a long time. Make the most of them while they're new.
In addition, Li-ion batteries must be stored in a charged state. If stored for a long time in a deeply discharged state, they fail.
Li-ion batteries are the most expensive today. Improving their production technology and replacing cobalt oxide with a less expensive material could lead to a reduction in their cost by up to 50% over the next few years.
Lithium polymer batteries.
In the international interpretation, the designation is accepted as LITHIUM POLIMER BATTERY or Li-Pol for short.
Lithium polymer batteries are the latest innovation in lithium technology. Having approximately the same energy density as Li-ion batteries, lithium-polymer batteries can be manufactured in various plastic geometric shapes that are unconventional for conventional batteries, including those that are quite thin in thickness and capable of filling any free space in the equipment being developed.
This battery, also called "plastic", is structurally similar to Li-ion, but has a gel electrolyte. As a result, it becomes possible to simplify the design of the cell, since any leakage of electrolyte is impossible.
Li-pol batteries are beginning to be used in laptop computers and cell phones. For example, cell phones Panasonic GD90 and Ericsson T28s (GSM 900/1800 standard) are equipped with lithium-polymer batteries only 3 mm thick and have a capacity sufficient to operate for 3 hours in talk mode and up to 90 hours in standby mode.
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