What is battery equalization charge? Procedure for using rechargeable batteries How to equalize the voltage in the battery banks

When battery stacks operate in buffer or cyclic mode, as well as when such systems are expanded, an uneven distribution of electrical energy output is possible, which leads to faster battery aging. Read this article on how to properly level the battery charge.

Periodic leveling electric charge batteries in the system is a necessary process to ensure correct work equipment. If several batteries are connected in a circuit, imbalance may occur over time - a noticeable change in the voltage of individual batteries. To avoid this, it is recommended to rebalance once every six months. It is usually carried out using increased voltage for twenty-four hours. You can find out the specific voltage from the battery specification on our website, look at the data on the manufacturer’s website, or check with the seller.

Multi-level systems - brief description and purpose

Systems using multiple batteries, are widely used in everyday life and in production. About diagrams for connecting batteries in multi-level systems. Here it must be said that they are very useful for long-term provision of uninterrupted power supply to heating boilers, as well as for creating “green” energy systems powered by solar panels and wind generators. After all, in addition to generating electricity, it must also be accumulated and stored somewhere. It is for these purposes that systems of several rechargeable batteries are needed, with the help of which a system of any capacity and voltage can be assembled from 12-volt batteries.

As mentioned above, during long-term operation problems arise related to battery imbalance; later we will talk about this in more detail.

In order to avoid charge imbalance in new batteries, it is recommended to buy all batteries from the same manufacturer, the same series, type and capacity with the same release date. If these rules are violated or the system is expanded, the battery charge must be equalized!

If during system service uninterruptible power supply If there is a need to expand the capacity, then the most ideal option would be to select an additional battery based on the above requirements, no more than a year apart in the date of release.

The fact is that a year after the operation of such a system, irreversible processes may occur in deep-discharge lead-acid batteries and their normal joint operation is not guaranteed. Those. A new battery can be damaged by older ones. If there is a significant difference in the production date of a year or more, the manufacturer's after-sales warranty for the new battery may be lost!

Imbalance - what is it and how to deal with it

From time to time, in all systems using batteries with serial, parallel or mixed connection types, charge imbalance occurs. Because of this, battery performance deteriorates, capacity decreases, and individual batteries fail before their design date.

The problem is that all batteries are slightly different from each other, even if they are the same brand. When creating a battery pack, these differences may increase. Suppose there is a battery in the system with a resistance slightly higher than its neighbors. Naturally, when charging, the voltage on it will be slightly higher, and the overvoltage protection may even work. When discharging electricity, the voltage of this battery will be the lowest, as will its capacity. All this leads to the fact that the resource of the entire system will not be fully used. The result is degradation and strengthening of the defect over time. A weak link will degrade the performance of the entire battery pack. You can, of course, buy another battery, but this is not a panacea. What to do if the batteries are relatively new? And the cost is not cheap.

There are two ways to equalize battery charge:

Passive;
Active.

The first method uses bypass circuits that disperse energy. These devices can be built into the UPS system, or located in a separate chip. Most often, this method is used in budget equipment. Almost all excess electrical energy from a battery with a superior charge is converted and dissipated - this is the main limitation of the passive method. It reduces the life of the system without charging.

With the active balancing method, inductance is used to transfer electricity from batteries with a higher charge to weak batteries, therefore, losses are not high. Thanks to this, the active method is much more effective than the passive one. But you still have to pay extra for quality; active equipment is more expensive.

Battery charge equalization - practice

A system that equalizes the battery charge is necessary for Maintenance Batteries with a serial connection type, when charging them from a single source. Batteries connected in series form a single circuit or line. There may be several of them, depending on the nature of the system. The equipment is capable of regulating currents on individual batteries in several circuits simultaneously.

The system consists of a controller, which is responsible for regulating the charge. It connects to the general power source of the circuit. There are also separate sensors installed on the battery. This equipment is switched using a special loop.

Batteries in one circuit must be of equal capacity, otherwise the equipment will not cope with the task of balancing the charge on the batteries. The greater the difference in capacitance characteristics, the more charge and discharge cycles will be required to equalize the battery charge.

How the charge balancer works

The controller analyzes the voltage and starts if it increases. The system calculates the average and, using special loops, takes information from each individual battery. If the battery voltage exceeds the average, the controller issues a command for load compensation. If it is lower, the load is removed. These actions are tied to charge-discharge cycles, and, with each new cycle, the voltage is brought to the average.

If the total electrical voltage does not increase over three working hours, the controller signals that the work is completed and issues a command to turn off the sensors on the battery. But, the analysis of electrical voltage does not stop.

All batteries are equipped with a voltage sensor-controller. It is best to do this next to the contacts, then connect the plus to the plus, the minus to the minus. When installed correctly, the sensor flashes. If there is no signal, either it was connected incorrectly, or the battery is faulty. Via the COM port, the controller can output information on each battery to a personal computer.

In addition, the controller signals when the battery voltage drops or rises below 10.5 Volts and above 15 Volts.

conclusions

Equalizing battery charges is a necessary technical measure. It increases the safety of using batteries and increases their service life. Modern battery balancing controllers are tested technical condition each battery and make it possible to use the system while minimizing losses. In general, this is useful for safety reasons and ensures reliable and trouble-free operation of the equipment.

Category: Charger support Published 05/04/2016 12:06

Most stationary batteries use a lead-acid electrochemical system, which requires some maintenance, including an equalizing charge. Periodic application of an equalizing charge allows the characteristics of all cells to be equalized to the same level by applying a charging voltage of 2.50 V per cell, which is about 10 percent higher than the normal value.

An equalization charge is nothing more than a deliberate overcharge to remove lead sulfate crystals from the plates that have accumulated over time. If you do not control the battery condition, the processes sulfation may reduce the overall capacity or even damage the battery. The equalizing charge also combats acid stratification- a condition in which the acid concentration at the bottom of the battery becomes higher than at the top.

Experts recommend performing a maintenance equalization charge once or twice a year. The best method to find out about its need is to use a full charge in saturation mode, with further comparison specific gravity each cell of a flooded lead-acid battery using a hydrometer. If the difference between the specific densities of different elements is more than 0.030, then this indicates the need to use an equalizing charge.

During the equalization charge, check the specific gravity of the cells every hour and do not stop charging until the density stops increasing. Stopping the increase in density will indicate that no further improvements in the battery are possible, and further charging can only do harm.

The battery being charged must be kept in a cool place and under constant attention - excessive heat and gas formation is possible. Moderate gas formation is normal, but in any case the battery must be charged in a ventilated area, since only a 4 percent concentration of hydrogen in the air is already explosive.

There is no general agreement on the advisability of applying an equalizing charge to VRLA and other sealed batteries. Some manufacturers recommend equalizing the charge of such batteries monthly for 2-16 hours. But it should be remembered that overcharging sealed batteries leads to excessive gas formation and activation of the 34 kPa valve, which can result in electrolyte depletion.

Not all chargers have an equalizing charge function. Such a charge should not be carried out with a device not intended for this purpose.

Carry out an external inspection of the battery. The top surface of the battery and terminal connections must be clean and dry, free from dirt and corrosion.
If there is liquid on the top surface/of the flooded batteries, this may indicate that there is too much liquid in the battery. If there is liquid on the surface of a gel or AGM battery, this means excess battery charge, and its performance and service life will be reduced.
Check battery cables and connections. Replace damaged cables. Tighten loose connections.

Cleaning

Make sure all protective caps are securely attached to the battery.
Clean the top surface of the battery, terminals and connections using a rag or brush and a solution of baking soda and water. Do not allow cleaning solution to get inside the battery.
Rinse with water and dry with a clean cloth.
Apply a thin layer of petroleum jelly or terminal protectant, available from your local battery supplier.
Keep the area around batteries clean and dry.

Adding water (ONLY batteries with liquid electrolyte)

It is forbidden to add water to gel or AGM batteries, since they do not lose it during operation. Water needs to be added periodically to flooded batteries. The frequency of topping up depends on the nature of battery use and operating temperature. New batteries should be checked every few weeks to determine the frequency of topping up water for a specific application. Batteries typically require more frequent toppings as they age.

Fully charge the battery before adding water. Add water to discharged or partially charged batteries only if the plates are visible. In this case, add just enough water to cover the plates, then charge the battery and continue the water refill process described below.
Remove the protective caps and turn them over to prevent dirt from getting on the inside surface. Check the electrolyte level.
If the electrolyte level is significantly higher than the plates, then it is not necessary to add water.
If the electrolyte level barely covers the plates, add distilled or deionized water to a level 3 mm below the ventilation well.
After adding water, install the protective caps back on the battery.
Tap water can be used if the level of contamination is within acceptable limits.

Charge and equalization charge

Charge

Proper charging is extremely important to get the most out of your battery. Both undercharging and overcharging a battery can significantly shorten its service life. For proper charging, see the instructions included with the equipment. Majority chargers-automatic and pre-programmed. Some chargers allow the user to set the voltage and current values. See charging recommendations in the Table.

Make sure the charger is set to the correct program for wet, gel or AGM batteries, depending on the type of battery you are using.
The battery must be fully charged after each use.
Lead-acid batteries (wet, gel and AGM) do not have a memory effect and therefore do not require a complete discharge before recharging.
Charging should only be carried out in well-ventilated areas.
Before charging, check the electrolyte level to ensure that the plates are covered with water (wet batteries only).
Before charging, make sure that all protective caps are securely attached to the battery.
Batteries with liquid electrolyte will release gas (bubbles) before completing the charging process to ensure the electrolyte is properly mixed.
Do not charge a frozen battery.
Charging should be avoided at temperatures above 49°C.

Scheme 4

Scheme 4 and 5

Equalizing charge (ONLY for wet batteries)

An equalization charge is a battery overcharge performed on wet batteries after they have been fully charged. Trojan recommends an equalization charge only if the batteries have a low specific gravity, less than 1.250, or the specific gravity fluctuates within wide range, 0.030, after full charge battery Do not equalize charge GEL or AGM batteries.

You must make sure that the battery is a wet battery.
Before starting charging, check the electrolyte level and make sure that the plates are covered with water.
Make sure that all protective caps are firmly attached to the battery.
Set the charger to equalizing charge mode.
During the equalizing charge process, gas will be released in the batteries (bubbles will float to the surface).
Measure the specific gravity every hour. The equalizing charge should be stopped when the specific gravity stops increasing.

ATTENTION! It is prohibited to perform an equalization charge on gel or AGM batteries.

8.1. Constant charging mode.

All AB in electrical networks and substations must be operated in constant recharging mode.

A fully charged battery must be connected to the buses in parallel with a constantly running charging unit. The charging unit supplies the load direct current and at the same time recharges the battery, compensating for its self-discharge. End AEs must also operate in constant recharge mode.

When a powerful jolt load is turned on, as well as when the charging unit loses power from the alternating current side, the battery takes over the entire load of the DC network.

In emergency modes, the battery must also ensure operation necessary equipment ES or PS for at least 1 hour with the required voltage level of the design mode.

For an SK type battery, the charging voltage should be 2.20 ± 0.05 V per AE.

For SN type batteries, the recharge voltage should be 2.18 ± 0.04 V per AE at an ambient temperature not exceeding 35 °C. If the temperature is higher, the voltage should be 2.14 ± 0.04 V.

For batteries different companies, which use the main types of batteries (Vb VARTA, OPzS, GroE, etc.), the recharge voltage should be 2.23 ± 0.005 V per AE at an ambient temperature of 20 ° C. For other types of branded AEs (FIAMM, OGi, etc.), the charging voltage must meet the requirements technical documentation to a specific type of AE of the manufacturer, supplier ((2.27 ± 0.03) V; 2.27 V ± 1%; 2.23 V ± 1%, etc.).

The voltage spread across individual AEs within the battery in the recharging mode should not exceed plus 0.1 V/minus 0.05 V from the recharging voltage.

The spread of electrolyte temperatures should be no more than 3°C compared to the average temperature of the battery electrolyte. The average temperature of the battery should not exceed the temperature of the ambient air (medium) by 3 °C.

The charging installation must ensure stabilization of the voltage on the battery with deviations that do not exceed the requirements established by the manufacturer, and for branded batteries - no more than ± 1% of the rated voltage (or the requirements established by supplier companies).

The specific current and voltage values required cannot be set ahead of time. It is necessary to establish and maintain an average value of the charging voltage and monitor the battery. A decrease in electrolyte density in most batteries indicates insufficient recharging current. In this case, as a rule, required voltage recharging is 2.25 V for SK type batteries and not lower than 2.20 V for CH type batteries.

8.2 Charge mode.

Subject to compliance with operating requirements, and also depending on the condition of the battery, local conditions, the availability of appropriate types of chargers (units), and the availability of time, it is permissible to use any known charging methods and their modifications:

at constant current;
with a smoothly descending current strength;
at constant voltage, etc.

The charging method is established by the company's instructions.

In this case, there should be no conditions under which, for specific types of AE, unacceptable voltages and charge currents, excess of the electrolyte temperature and processes of intense gas formation may occur.
During charging, the necessary parameters to monitor the condition of the batteries should be measured and recorded at appropriate intervals.

Charging at a constant current must be performed in one or two degrees.

With a two-stage charge, the first stage current should not exceed 0.25C10 for SK type batteries, 0.2C10 for CH type batteries, and 0.7C10 for branded batteries, depending on the type (until a voltage of 2.40 V is reached at the AE).

When the voltage increases (reaches) up to 2.30-2.35 V/cell. for conventional and 2.40 V on AE for branded ones, the charge is transferred to the second stage, the charge current should be no more than: for batteries of type SK - 0.12C10, for batteries of type SN - 0.05C10 and for branded batteries - 0, 35С10.

With a single-stage charge, the current should not exceed a value equal to 0.12C10 for batteries of types SK and CH and 0.15C10 for branded batteries. Charging SN type batteries with a current of 0.12C10 is allowed only after emergency discharges.

The charge is carried out to a constant voltage and electrolyte density for 1 hour for SK type batteries and for 2 hours for SN type batteries.

Branded batteries are charged to a constant voltage of 2.6-2.8 V/cell. and electrolyte density 1.24 ± 0.010 g/cm3 (reduced to a temperature of 20 °C) for 2 hours.

When charging branded batteries using a gradually decreasing current method until a voltage of 2.4 V/cell is reached. charging current is not limited. At a voltage of 2.40 V/cell. the charge current should not exceed 0.15C10, and at a voltage of 2.65 V/cell. - 0.035С10.

Charging at a constant voltage must be carried out in one or two degrees.

The charge in one stage is carried out at a constant voltage of 2.15-2.35 V on AEs of conventional types SK and SN. In this case, the initial charge current may exceed the value of 0.25C10, but then it automatically decreases to the level of 0.05C10.

Branded batteries are charged at a constant voltage of 2.25-2.30 V/cell, with the initial charge current being (0.1-0.3)C10.

Charging in two stages of conventional types is carried out in the first stage with a current that does not exceed 0.25C10, up to a voltage of 2.15-2.35 V on the AE, and then at a constant voltage - from 2.15 to 2.35 V/cell.

Branded batteries at the first stage are charged with a current of (0.1-0.15)C10 until a voltage of 2.35 V/cell is reached, and at the second stage it is maintained constant pressure charge 2.23 V ± 1%, while the charge current automatically gradually decreases. The charge ends when the voltage and density of the electrolyte on the AE reach constant values for 2 hours.

Charging batteries with an elemental switch must be carried out in accordance with the instructions of the enterprise.

During charging, the voltage at the end of the charge can reach 2.60-2.70 V/cell; the charge is accompanied by strong “boiling” of the battery electrolyte, which will cause increased wear of the electrodes and a reduction in service life, especially for branded batteries.

For all charges, the batteries must have at least 115% of the capacity removed from the previous discharge.

During charging, it is necessary to measure the voltage, temperature and density of the battery electrolyte in accordance with Table 8.

Before turning on, 10 minutes after turning on and after the end of charging, before turning off the charging unit, it is necessary to measure and record the parameters of each battery, and during charging - of the control batteries. The charge current, cumulative capacity and charge date are also recorded.

The electrolyte temperature during charging of SK type batteries should not exceed 40°C. At a temperature of 40°C, the charging current must be reduced to a value that will ensure the specified temperature.
The electrolyte temperature during charging of CH type batteries should not exceed 35°C. At temperatures above 35°C, the charge is carried out with a current that does not exceed 0.05C10, and at temperatures above 45°C - with a current of 0.025C10.

In branded batteries such as Vb VARTA, OPzS, GroE, etc. In accordance with the requirements of the specifications and technical documentation, during charging the electrolyte temperature is not allowed to rise above 55 °C.
When charging CH type batteries (as well as branded batteries that use special filters and valve-controlled linings) with a constant or gradually decreasing current, it is necessary to remove the ventilation filter plugs.

8.3. Equalizing charge.

The same charging current, even at the optimal battery charging voltage, due to the difference in self-discharge of individual batteries, may be insufficient to maintain all batteries in a fully charged state.

To bring all SK type batteries to a fully charged state and to prevent sulfation of the electrodes, it is necessary to carry out an equalizing charge with a voltage of 2.30-2.35 V/cell. until the electrolyte density in all batteries reaches a constant value of 1.20-1.21 g/cm3 at a temperature of 20 °C.

The frequency of battery equalization charges and their duration depend on the condition of the battery. An equalizing charge must be carried out at least once a year for at least 6 hours.

For those batteries where, due to the operating conditions of the electrical installation, the charging voltage can only be maintained at a level of 2.15 V per battery, an equalizing charge must be carried out quarterly.

For branded batteries, the need, frequency and conditions for equalizing charges are determined (agreed upon) in accordance with the technical documentation of the supplier companies for specific types of batteries.

When the electrolyte level drops to 20 mm above the protective shield of SN type batteries, add water and carry out an equalizing charge to completely mix the electrolyte and bring all batteries to a fully charged state.

The equalizing charge is carried out at a voltage of 2.25-2.40 V/cell. until the electrolyte density in all batteries reaches a constant value of 1.240 ± 0.005 g/cm3 at a temperature of 20°C and its level is 35-40 mm above the safety shield.

The duration of the equalizing charge is approximately:

at a voltage of 2.25 V - 30 days;
at a voltage of 2.40 V - 5 days.

If, when monitoring the voltage on the AE, its deviation exceeds the average value by ± 0.05 V, it is necessary to additionally monitor the density of the electrolyte in this AE (and correct it if necessary).

If the battery has single batteries with reduced voltage and reduced electrolyte density (lagging batteries), then an additional equalizing charge is carried out for them from a separate rectifier device.

8.4. Battery discharge.

Batteries that operate in constant recharge mode are practically not discharged under normal conditions. They are discharged only in the event of a malfunction or disconnection of the recharging device, in emergency conditions or during control discharges.

Individual batteries or groups of batteries are subject to discharge during repairs or troubleshooting.

For a battery on a substation, the estimated duration of emergency discharge is set to at least 1 hour. To ensure the specified duration, the discharge current should not exceed the values of 18.50 x No. A and 25 x No. A, respectively.

For branded batteries, the calculated discharge current is determined according to the technical documentation for a specific type of battery.

When discharging batteries with currents less than the 10-hour discharge mode, it is not allowed to determine the end of the discharge only by voltage. The end of the discharge is determined by the following conditions:

reduction in electrolyte density to 1.15 g/cm3 (by 0.03-0.06 g/cm3 compared to the electrolyte density at the beginning of the discharge);
voltage reduction to 1.80 V;
removing the container after 10 hours.

8.5. Control digit.

Control discharges of one of the most lagging AEs or checking the performance of the AE with a jog current must be performed according to a duly approved program.

Control discharges must be performed to determine the actual capacity of the battery and carried out in a 10-hour or 3-hour discharge mode.

The discharge current value should be the same each time, but not higher than the maximum permissible for a particular type of battery.

For batteries (AE), which are used in the industry, the final voltage of control discharges is 1.80 V/cell. during discharges with 10-, 5-, three-hour discharge current and 1.75 V/el. — during discharges with one-hour and 0.5-hour discharge current.

Branded batteries allow deeper discharges at final voltages, however, in order to unify the requirements for the period of mastering and gaining operational experience, the final voltage of the 10-hour control discharge is set to 1.80 V/cell.

At the PS, control discharges are carried out if necessary. In cases where the number of batteries is insufficient to provide voltage on the busbars at the end of the discharge given boundaries, it is allowed to discharge part of the main batteries.

Control discharges of branded batteries type Vb VARTA, OPzS, etc. are carried out in accordance with the requirements of technical documentation (TS) of supplier companies, but at least once every five years. If a trend towards a decrease in the actual capacity of the battery below the nominal is detected, control discharges can be performed every six months.

Before the control discharge, it is necessary to equalize the batteries.

The measurement results of the control discharge must be compared with the measurement results of the previous discharges. For a more correct assessment of the condition of the battery, it is necessary that all control discharges of a given battery be carried out in the same mode and entered into the battery log.

Before starting the discharge, it is necessary to record the discharge date, voltage, electrolyte density of each battery and the temperature in two or three control batteries.

During discharge on control and lagging batteries, voltage, temperature and electrolyte density should be measured in accordance with Table 9.

Table No. 9

During the last hour of discharge, the battery voltage must be measured every 15 minutes.

The test discharge must be carried out to a voltage of 1.8 V on at least one battery. For some types of branded batteries, the company's instructions may state that the control discharge should be stopped after the terminals of the battery poles reach the final discharge voltage n x 1.8 V or after the corresponding time has elapsed (10 hours).

At the end of the discharge, it is necessary to take electrolyte samples from control batteries for chemical analysis and checking the content of impurities in accordance with GOST 667-73, GOST 6709-72, PUE or in accordance with the requirements of supplier companies.

After the first year of operation of batteries of type SK, SN, electrolyte analysis must be performed from all batteries.

At the end of the discharge, the voltage, temperature and density of the electrolyte, as well as the voltage between the battery poles and between the battery poles and the ground, should be measured and recorded for all AEs.
If the average temperature of the electrolyte during discharge differs from 20 °C, then the resulting actual capacity must be reduced to the capacity at a temperature of 20 °C according to the formula:

C20 = SF/1+ α(t-20), where

C20 - capacity reduced to a temperature of 20°C, A x hour;
SF - capacity actually released during discharge, A x hour;
α - temperature coefficient, in accordance with table 10;
t is the average temperature of the electrolyte during discharge, °C.

Table No. 10.

8.6. Topping up batteries.

The electrodes in the AE must always be completely recessed into the electrolyte.

The electrolyte level in SK type batteries must be maintained 10-15 mm above the top edge of the electrodes. If the electrolyte level decreases, you need to top up the batteries with distilled water, tested to be free of chlorine and iron. It is allowed to use steam condensate in accordance with GOST 6709-72. Water can be supplied to the bottom of the tank through a tube or to its upper part. In the latter case, it is recommended to recharge the battery with “boiling” to equalize the density of the electrolyte.

Batteries with an electrolyte density below 1.20 g/cm3 can be topped up with an electrolyte with a density of 1.18 g/cm3 only if the reasons for the decrease in density are identified.

The electrolyte level in SN type batteries should be between 20 and 40 mm above the safety shield. If topping up occurs when the level drops to the minimum limit, it is necessary to carry out an equalizing charge.

Under normal operating conditions, some batteries (Monolit type, SMG, etc.), especially those with valve regulation (VRLA type, etc.), do not need to be topped up with electrolyte throughout their entire service life. For some types of batteries (VARTA, etc.), refill intervals can be more than three years.

It must be borne in mind that most often, at a lower electrolyte level, the density of the electrolyte increases, so distilled water of the appropriate quality should be added (GOST 6709-72). It is necessary to add water no later than when the electrolyte level drops to the lower level. permissible level. In branded batteries, the electrolyte is added to a level that is 5-10 mm below the applied maximum permissible level “max”.

To achieve homogeneity of the electrolyte, it is necessary to perform an equalizing charge.