Market in Costa Rica
Most of the batteries and accumu- lators used in the country are impor-ted, the figure shown on the right side presents the acquisition of theseduring the period from 2010 to 2018 where it is observed that most of the purchases made are from energy accumulators with higher growth in the last four years.
Import data for these devices can befound on the Ministry of Finance's website, which can be accessed by clicking on the link.
Imports of batteries into Costa Rica are from different countries around the world, among the major importing countries in 2010 as shown in the figure on the left side are the United States, Mexico, China and Thailand, where the latter had the largest amount of imports into the country.
However, if you look at the figure on the right side, in 2018, the direction of imports took a turn, where you can see that the largest importer is China, followed by the United States, Mexico and Panama. These markets are currently booming in terms of batteries.
On the other hand, imports of accumulators into Costa Rica are also made from different countries around the world, where it can be seen in the figure on the left side that in 2010, the main countries from which these devices were imported were Mexico to a greater extent, Indonesia and China.
While for 2018, as shown in the figure on the right side, the main imports that weremade were from Mexico, the United States and China, maintaining to a greater extent the trend observed since 2010.
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Battery tests
Depending on the construction and the use given to the battery, these have a lifespan ranging from a few years to ten years or more, among the main reasons for aging and failure of batteries are :
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Sulphation: when a battery is discharged, the active mass of the positive and negative plates is transformed into small sulphate crystals, which, if left discharged, tend to grow and harden forming an impenetrable layer that cannot become active material, thus producing a decrease in the capacity of the battery to the point where it stops working.
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Positive plate corrosion: this takes place while the battery is being recharged, especially in the charge cycle when the battery voltage is high, it is a slow but continuous process, oxidation increases the internal resistance of the battery thus causing the disintegration of the positive plates.
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Shredding of active material: this phenomenon occurs mainly when the battery is subjected to intensive charge and discharge cycles, the effect of the repetitive chemical transformation of the active material on the plates tends to reduce the cohesion so that the active material falls from the plates depositing at the bottom of the device.
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Operating conditions: the temperature to which they are subjected and the speed of charging and discharging are a factor that greatly influences the aging of batteries, so that high temperatures and high charging speeds accelerate the aging of the batteries.
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Carbonation: this is caused by the absorption of carbon dioxide in the air by the electrolyte, is a phenomenon that occurs gradually and is reversible.
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Flotation effects: the loss of capacity in the battery due to long periods of flotation without cycles, this can cause catastrophic failures in the load supported, however, the effects of flotation are reversible by discharging the battery to zero between one or two times.
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Positive plate iron poisoning: this is caused by corrosion on the plates and is an irreversible phenomenon.
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Soft and hard shorts: these shorts occur for several reasons, the hard shorts are usually caused by pieces of paste pushed by the current producing a short in the adjacent plate (opposite polarity), the soft shorts on their part, are caused by deep discharges, this failures cause the impedance to drop and the float voltage to drop slightly.
Due to these problems there are different tests that can be performed on a battery to determine its quality and condition, in order to take corrective or preventive action for them and thus avoid possible damage or malfunction in equipment or applications in which these devices are used.
Before performing any type of test on a battery, the device should be inspected to identify visual defects such as lumps, corrosion on connections, surface moisture, low electrolyte level, among others. Once the visual inspection has been carried out, the following tests can be carried out, these will be carried out in periods established by the IEEE standards relevant to each type of battery, where they can range from monthly to annual tests.
Capacity
Test
The capacity test is the only way to obtain an accurate value of the current capacity of the battery, if this is used regularly, can serve to check the health of the battery and estimate the remaining life of this. Each battery has a table with the discharge current for a specific time until a specific end of discharge voltage.
During the test what is done is to measure how much capacity (current per time in Ah) the battery can supply before the terminal voltage drops to the end of the discharge voltage per number of cells. In this test the current should remain constant and it is recommended to use a test time that is approximately the same as the service cycle of the battery.
Impedance
Test
This is an internal ohmic test, i.e. it measures the resistance of the battery in terms of alternating current. This test shows the condition of the battery without damaging it or subjecting it to stresses of any kind as it is testing the condition of the entire electrical passage of the battery from terminal plate to terminal plate. The impedance test can find weaknesses in cells and connectors in an easy and reliable way.
Impedance is determined by applying an alternating signal current to the terminal boards, measuring the voltage drop along the cell or connector between cells and calculating impedance using Ohm's law. In practice, not only is the voltage drop measured, but also the current, which is measured by means of other AC currents in the battery that are additive.
Temperature
Test
The temperature is the factor of greater incidence that shortens the useful life of the same ones, it is known that the low temperatures reduce the internal chemical reactions in any battery and therefore reduce their performance, on the other hand, the high temperatures can ruin the batteries. Applying Arrhenius' conclusions on chemical reactions, we have that for every 10℃ increase in battery temperature this reduces its useful life by half and therefore must begin to be treated.
Increased temperatures cause corrosion in the positive grids more quickly, which leads to other types of failures, once the positive grids corrode, they cannot be recovered. Corrosion of these grids occurs at any temperature, however, the speed of corrosion will be greatly influenced by the temperature, therefore, should be controlled as best as possible, the temperature to which the batteries are exposed in the network.
Abnormal load
Test
This is carried out by measuring the tolerance of the battery when exerting a rate of overcharge current on it in a given time.
External short-circuit
Test
For this test it is required to connect externally the cathode and the anode, so that a maximum current is passed, so that the ability to resist this flow is measured.
Reverse load
Test
The aim is to analyse the behaviour of a battery when it is charged with an inverse polarity current for one hour. This must be done under the parameters of IEC 62133, UL Subject 2271 and UL 2580.
Insulation resistance
Test
This test subjects a cell to a resistance between the terminal of each battery and the accessible metal of all batteries, this measurement must correspond to a value greater than the specified minimum resistance.
Forced discharge
Test
It studies the behavior of a battery that is discharged when it is in series with other similar batteries, which are charged, thus analyzing the resistance to the unbalanced series that is formed.
Security assessmente
Test
This test identifies risks, therefore ventilation systems, pressure systems, good functioning of safety equipment, an adequate fire control system, as well as tests to temperature control systems should be verified.