A. Why do batteries (groups) need regular maintenance and testing?
In the past, it was troublesome to maintain the open type battery, because the battery has to decompose the water in the electrolyte when it is in use, so it is necessary to test the specific gravity of the electrolyte, the voltage of the battery and other parameters on a regular basis, and the consumed electrolyte, it is necessary to add water regularly to replenish it.
After the emergence of sealed batteries, mainly valve regulated lead-acid batteries (mainly), because there is no need to add water, so the valve regulated lead-acid batteries from the beginning has been called maintenance-free batteries, and manufacturers have promised that the service life of the battery for 10 ~ 20 years (at least 8 years), which gives the domestic technology and maintenance personnel a misunderstanding, it seems that this battery is both durable and completely do not need maintenance, many users from the installation of the battery to the battery, and the battery is not maintenance-free, and many users from the installation of the battery, the battery is not maintenance-free. Need for maintenance, many users from the installation of the battery on the basic maintenance and management, and thus in the early 1990s the domestic use of VRLA batteries appeared a lot of new problems not previously encountered, for example, the battery shell deformation, electrolyte leakage, insufficient capacity, uneven voltage at the end of the battery and so on. These phenomena are not only in the country, but also in foreign countries that adopted VRLA batteries earlier than ours.
In the battery due to the electrolyte specific gravity is greater and the floating charge flow is greater, so the electrode corrosion is more rapid. Electrode corrosion also consumes oxygen and dries out the battery, a failure unique to VRLA batteries. Electrolyte leakage can be caused by excessive gas escaping from the battery, cracks in the welded posts or covers, poor sealing, and finally water, hydrogen, and oxygen seeping through the walls of the container and the plastic container.Some of the failures of VRLA batteries are caused by malfunctioning gas regulator valves, and the cooling of VRLA batteries is even more important than that of open-ended batteries, as thermal runaway can cause the batteries to melt or explode if it is not adequate.VRLA batteries have internal terminals, same-pole terminals, and other components of the battery. VRLA batteries also break more often than open cell batteries due to corrosion of the internal terminals, connecting tabs on the same poles, and electrode connectors. All of these failures result in loss of capacity. This makes it difficult for users to grasp the durability and failure of VRLA batteries.
Practice has proved that the VRLA battery terminal voltage and discharge capacity has no correlation, VRLA batteries and battery packs in the process of operation, with the increase in the use of time will inevitably be individual or part of the battery due to the internal resistance of the battery becomes large, the phenomenon of degenerative aging, practice has proved that the capacity of the whole battery is in the worst condition of the battery capacity value shall prevail, rather than the average or rated value (initial value) When the actual capacity of the battery drops to below 90% of its own rated capacity, the battery will enter the recession period, when the battery capacity drops to below 80% of the original, the battery will enter a sharp decline in condition, the recession period is very short, and the battery group are connected in series, if there is a section of the problem, then the whole group will be invalidated, this time the battery group has been a great potential danger of accidents.
Using units and management units, often only pay attention to the maintenance and management of the equipment part of the backup power supply, while ignoring the significant role of the battery pack, unaware of the danger of power outages to a large extent on the lurking in the battery pack. The characteristics of the whole battery charging, such as battery packs, one or more internal resistance of the aging battery, its capacity is bound to become smaller, the charger to the battery pack charging, aging batteries due to the capacity of small, will soon be full. The charger will mistakenly think that the whole group of batteries has been filled and turned to float charging state, with a constant voltage and small current to the battery pack charging. The remaining batteries in good condition are unlikely to be full. The battery pack will be charged and discharged with the capacity of the aging batteries, and after many vicious cycles of float charging-discharging-even charging-discharging-float charging, the capacity will keep dropping and the battery backup time will be shortened.
Conclusion: If we don't test regularly and find out the aging batteries and adjust them, the capacity of the battery pack will become smaller, and the life of the batteries will be shortened, which will affect the efficient and safe operation of the system.
B. What are the problems encountered when using?
Problems with Battery Use
Electrode Corrosion is More Rapid: VRLA batteries have a higher specific gravity of the electrolyte and a higher float charge current Battery Dryness: Electrode corrosion can also consume oxygen, which can dry out the battery Electrolyte Leakage: Excessive gases escape from the VRLA batteries, welded columns or cracked caps, poor sealing, and finally water leaks out through the walls of the containers and the plastic containers, Hydrogen and oxygen Malfunctioning gas regulator valves: Open valves can lead to drying out and also allow air to enter the battery, cathode plates to self-discharge, and clogged valves can cause the lid to bulge out and explode Battery meltdowns or explosions: Cooling of VRLA batteries is much more important than in open-ended batteriesCorrosion of the internal terminals, connecting tabs on the same poles, and electrode connectors and their rupture are more common in VRLA than in open-ended batteries.
All these will lead to capacity loss
C. Why do we need a battery internal resistance tester?
Traditional battery capacity testing method is to carry out a whole group of checking discharge, that is, the battery group connected to the load box, and then discharge, has been put to the cut-off voltage (no power) until, to verify the capacity of the battery, but this method has a lot of hidden dangers and shortcomings:
a, electric time is long, the risk is great, the battery pack must be separated from the system, the chemical energy stored in the battery pack is consumed in the form of heat energy, both in the form of heat energy, and in the form of heat energy, and in the form of heat energy, and in the form of heat energy. Consumed in the form of heat energy, both a waste of electrical energy and time-consuming and inefficient.
b, the check discharge test, must have certain conditions, first, as far as possible in the utility basic security conditions; second, there must be a backup battery pack.
c, verification discharge can only test the whole battery capacity, can not test the capacity of each individual battery, the lowest capacity of a section as a whole group capacity, and other parts of the battery due to the depth of discharge is not enough, the deterioration or backwardness of the degree of can not be fully exposed.
d, loss of battery capacity. As the internal chemical reaction of the battery is not fully reversible. The number of full-depth cyclic discharge is limited, so it is not suitable for lead-acid batteries frequently deep discharge. But the interval time is too long, the state of the battery between two checks is uncertain. After the capacity of the battery drops below 80%, the battery enters into a sharp decline condition, and the decline period is so short that it may fail in a few months after a check discharge, and in the remaining time the battery pack has existed a great potential risk of accidents.
Principle of internal resistance test:
Through a large number of tests, it is concluded that: the internal resistance value of the battery rises as the capacity of the battery decreases, that is to say, when the battery is aging and the capacity is decreasing, the internal resistance of the battery will be increasing. Through this test result, we can conclude that by comparing the internal resistance value of the whole group of batteries or tracking the degree of change of the internal resistance of a single battery, we can find out the backward batteries in the whole group, and by tracking the degree of change of the internal resistance of a single battery, we can understand the degree of aging of the batteries, so as to achieve the purpose of maintaining the batteries.
For VRLA batteries, if the internal resistance increases by more than 20% compared to the baseline value (average value), the battery performance will drop to a lower level. This value is also the IEEE STD recommendation for immediate corrective action (discharge test or replacement), and the IBEX1000 sets the alarm value at 20% based on this recommended benchmark.
Correspondingly, when a VRLA battery drops below 80% capacity, the battery ages like ?T in a graph, the time is unpredictable, and the rate of capacity degradation becomes more and more blocky, while the internal resistance increases more and more rapidly. Therefore, we recommend that you replace your batteries in a timely manner to improve the reliability of your company's battery system.
To date, the only practical way to determine the health of a battery is to use the standards recommended by the IEEE, so we recommend that corrective or replacement measures be considered when the internal resistance of a battery increases by more than 20%.
The internal resistance test has the following advantages:
a. Compact and lightweight, online measurement. Handheld internal resistance tester is small and portable, no need to remove the battery from the system when detecting the battery internal resistance, directly online testing, will not affect the power system work, to avoid power system risk.
b, small workload, easy to operate. The testing time of internal resistance tester is generally 2-3 seconds to test a battery, and the testing time for a group of 200 batteries is generally only about half an hour. As long as the battery is connected, the internal resistance tester will automatically test and save the data, so the operation is also very easy.
c, Timely discovery of backward batteries, in the maintenance staff to reduce the maintenance workload is increasing, through the internal resistance test can quickly find the backward batteries, improve the maintenance efficiency, to ensure that the system is safe and effective operation.
D. Can the internal resistance test completely replace the checking discharge test?
Checked discharge method is a 100% C deep discharge, which has the advantage of accurate and reliable capacity test, and therefore, it is still the most reliable method to test battery performance in the world. Check discharge method, i.e., the capacity test of full discharge, is the most direct and reliable method to detect the capacity of the battery. Whether the test is carried out on-line or off-line, a backup power supply must be set up as a precautionary measure to ensure the safety of the system.
The internal resistance test can be measured online without affecting the normal work of the system, while the test takes a short time and is very convenient for daily maintenance.
Because the internal resistance test is to check the aging degree of the battery by comparing the difference of the internal resistance of the whole group of batteries or tracking the change of the internal resistance of a single battery in different periods, it can't accurately measure the capacity 100%. However, since there are many drawbacks in checking discharge (see Knowledge Background C), the internal resistance test can make up for the drawbacks of checking discharge detection, and find out or predict the aging batteries by comparison, which makes the daily maintenance of the batteries very convenient and effective, and greatly saves the maintenance cost by looking for the laggard batteries and combining with the single battery discharge test, which makes the backup power supply system more stable and safe to operate.
E. What kind of method is used to measure internal resistance?
Direct current test: The battery is discharged to the test instrument, the voltage drop on the battery internal resistance is measured, and then divided by the discharge current to get the battery internal resistance, the general test current is very large, up to 50A-80A or so.
Advantages: Accurate testing, good consistency
Disadvantages: High testing current, must be connected to the probe and battery poles, if the contact is not good, it will arc, there are potential safety hazards.
AC test: the test instrument will add a known frequency and amplitude of the AC voltage signal at both ends of the battery, and measure the AC current value in the same phase with the voltage, and the ratio of the AC voltage component to the AC current is the internal resistance of the battery.
Advantages: The test method is simple, and will not affect the working condition of the battery, and will not produce safety hazards.
Disadvantages: 1, there is a susceptibility to charger ripple current and other noise sources interference.
2, some equipment can not be online (connected to the charger and load, and in the float state) on the battery test.
3, the use of 60Hz or 50Hz AC test current is more undesirable, because this is the main frequency of the charger ripple and noise sources.
Quick test of battery
------- analysis and application of battery internal resistance tester
Abstract: This paper compares the advantages and disadvantages of different kinds of battery testers which are widely used, and mainly introduces the principle and use of heterodyne battery internal resistance tester
Keywords: battery, heterodyne method, internal resistance, capacity
2. Battery maintenance
The small probability of damage to the battery is the world's unsolvable technical difficulties. Because of this the battery testing and maintenance is not only necessary, but also necessary!
The more common maintenance methods are:
First step: use the battery internal resistance tester to test the internal resistance of the battery on a regular basis, to find out the possible
undercapacity of the battery.
The second step: capacity verification with a battery discharge tester to find out the battery with insufficient capacity.
Step 3: Maintain or replace the battery with insufficient capacity.
3. Comparison of battery testers:
A Battery internal resistance tester:
Deducing the value of battery internal resistance.
B. Battery discharge tester:
The time (T) used to discharge the battery to the lowest allowable voltage of the battery through a certain current (I).Q=I*T The actual capacity of the battery is deduced.
4. Battery Internal Resistance Tester
ITB-712 series battery internal resistance tester adopts the most advanced, practical and technically difficult AC internal resistance technology (heterodyne method), and successfully realizes the accuracy and stability of the test data under the state of on-line charging and discharging by effectively overcoming the key technical difficulties of the AC method such as anti-noise and interference, which can be used for the promotion of early warning technology for battery failure. It provides high-performance professional technical equipment for the promotion of early warning technology of battery failure.
Features:
l The use of DDS, digital frequency selection, comb filtering and other new technologies to ensure that the test accuracy.
l Super anti-interference performance.
l Can test battery connection resistance
l Can test pure resistance (equivalent to microohmmeter).
l High-precision offline/online testing, large-capacity data storage.
l Adopting large LCD screen, the display interface is beautiful and easy to understand.
l Enhanced over-voltage protection function makes the instrument work more safe and reliable.
l Self-recovering overcurrent protection function makes the instrument more convenient to use.
l Small size, light weight, easy to operate.
l With test results print function
Technical Parameters: Measuring Range Internal (Connection) Resistance /: 0.000mΩ-99.99mΩ Minimum Measuring Resolution Internal Resistance: 0.001mΩ Measuring Precision Internal Resistance: ±1.5% ±6dgt Memory Capacity 2000 Sections Display 128×64 Dot Matrix Graphic LCD Operating temperature -1O℃～40℃ Relative humidity ≤90%RH Weight 3.6KG 5. Conclusion
Since the introduction of the battery internal resistance tester, widely used in electric power transmission units, coal mines, railroads, communications equipment rooms, unattended base stations and other units. With the enhancement of people's awareness of conservation, battery maintenance testing will be more and more attention. Battery tester will produce greater economic and social benefits.
Comparison of battery testers:
A Battery Internal Resistance Tester:
The correlation between internal resistance and capacity is: when the internal resistance of the battery is greater than 25% of the initial value (base value), the battery will not be able to pass the capacity test. When the internal resistance of the battery is greater than 2 times of the initial value, the capacity of the battery will be below 80% of its rated capacity. Based on this, the battery internal resistance tester mainly adopts the internationally popular heterodyne method (AC test method) to test, by adding a specific AC signal (I) to the battery, and then using a high-performance band-pass filter to detect the voltage drop on the internal resistance of the battery (U), R = U/I
The value of the internal resistance of the battery is deduced.
This method is easy to test, regardless of whether the battery is fully charged or not. It can be tested online or offline, and the test speed is fast, suitable for large-scale testing. (Especially the online test, completely avoid the test may cause the battery can not work, and thus lead to the system paralyzed situation!)
B. Battery Discharge Tester:
The time (T) used to discharge the battery to the lowest permissible voltage of the battery through a certain current (I).Q=I*T to derive the actual capacity of the battery.
This method can only be used for offline testing, and it takes a lot of work to remove the battery; the battery to be tested must first be fully charged, which takes a longer time to charge; then the test can begin, which takes a longer time to discharge.
The battery must be charged immediately after the test is completed to prevent the utility power outage at this time. If a power failure occurs during the battery test, the system may be paralyzed