Characteristics, application and maintenance of valve-regulated lead-acid batteries

The battery has been invented by the French since 1859 and has a history of 143 years. In 1957, the United Kingdom first invented the re-combustion maintenance-free automotive battery. The German Sunshine Company invented the lead-density gel industrial lead battery. In 1983, the US GNB company invented and produced the I-type cathode absorption sealed lead-acid battery. In 1985, Japan YUASA The company began to produce MSE series large cathode absorption sealed lead-acid batteries. Subsequently, the UK developed the standard BS6290 part 4 (1987) lead-acid fixed type single-cell battery and battery pack (valve-controlled seal specification); IEC formulated the general requirements and test methods of IEC896-2 (1991) fixed-type lead storage battery, Part II: Valve-controlled; Japan has developed JISC8707-1992 sealed fixed cathode absorption lead storage battery; China Ministry of Posts and Telecommunications has developed YD/T799-1996 communication valve-regulated sealed lead-acid battery technical requirements and inspection methods; China The Ministry of Power formulated the technical conditions for ordering DL/T637-1997 valve-regulated sealed lead-acid batteries. The above standards have become the technical standards for product quality assessment.

Since the 1980s, a large number of foreign companies producing similar products have developed. In 1988, Shenzhen Huada Power System Co., Ltd. introduced the technology of GNB Company of the United States, and began to produce valve-regulated lead-acid batteries after digestion and absorption. Up to 12960Ah. In the 1990s, China produced similar products throughout the country.

1 valve-regulated lead-acid battery works

The design principle of the valve-regulated lead-acid battery is to inject the required amount of electrolyte into the plate and the separator. There is no free electrolyte. The negative electrode plate is moist to improve the ability to absorb oxygen. To prevent the electrolyte from decreasing, the battery is sealed. Therefore, the valve-regulated lead-acid battery is also called "lean battery".

The pole grid of the valve-regulated lead-acid battery mainly adopts lead-calcium alloy to increase the over-potential of the gas and gas (H2 and O2) of the positive and negative electrodes, so as to reduce the gas-discharging amount during the charging process. Oxygen begins to occur when the positive plate reaches 70% charge, and oxygen begins to occur when the negative plate reaches 90%. In the production process, the ratio of the thickness of the positive and negative plates is generally 6:4. According to the change of the mass ratio of the positive and negative active materials, when the velvet Pb of the negative electrode reaches 90%, the PbO2 on the positive electrode is close. 90%, after a little charge, the active materials on the positive and negative electrodes are respectively redoxed to 95%, which is close to full charge, which can reduce the precipitation of H2 and O2 gases. Ultrafine glass fiber (or silica gel) is used to absorb the electrolyte, and at the same time provide a channel for the diffusion of oxygen on the positive electrode to the negative electrode. Thus, once the oxygen diffuses to the negative electrode, it is immediately absorbed by the negative electrode, thereby suppressing the generation of oxygen on the negative electrode, causing more than 90% of the gas generated during the float charging process to be eliminated (a small amount of gas is discharged through the safety valve).

2 characteristics of valve-regulated lead-acid batteries

2.1 float charge

Floating charge voltage = open circuit voltage + polarization voltage

Figure 1 gas recombination efficiency

= (electrolyte specific gravity +0.85) + (0.10 ~ 0.18) V

=(1.30+0.85)+(0.10~0.18)V

=2.15V+0.10V

=2.25V

For example, the company's battery electrolyte has a specific gravity of 1.240 g/cm3, so its float voltage is 2.19V. Japan's YUASA company's float voltage is 2.23V.

2.2 float current flow

The floating charge current of a fixed acid-proof flameproof battery has two functions:

1) supplement the loss of self-discharge of the battery;

2) Provide current to the daily load.

The float-charge current of a valve-regulated lead-acid battery has three functions:

1) supplement the loss of self-discharge of the battery;

2) supply current to the daily load;

3) The float current is sufficient to maintain the oxygen circulation within the battery.

2.3 Terminal voltage deviation (static deviation and dynamic deviation)

The dynamic deviation is large at the beginning of the floating charge operation. In fact, the battery that has just been shipped may be due to the saturation of the electrolyte in some of the batteries, which affects the oxygen compounding reaction, so that the float voltage is too high, and the electrolyte saturated battery will decompose the water due to continuous charging. Automatically adjusted to the unsaturated state, the 6-month back-end voltage deviation gradually decreases. However, the large deviation does not exclude the manufacturing quality of some manufacturers.

China's GB13337.1-Q1 and Germany DJN43539-84 stipulate that the static deviation range of the fixed battery is +0.1~0.05V of the voltage average.

The Ministry of Posts and Telecommunications YD/T799-1996 stipulates that when static, the deviation between the highest voltage and the lowest voltage value is 20mV. When dynamic, the deviation between the highest voltage value and the lowest voltage value does not exceed 50mV.

The Ministry of Power DL/T637-1997 stipulates that when static, the deviation between the highest voltage and the lowest voltage value is 30mV. When dynamic, the deviation between the highest voltage value and the lowest voltage value does not exceed 50mV.

2.4 gas compounding

Under the normal floating charging voltage, when the current is below 0.02 C, the gas is 100% composite, and the oxygen deposited by the positive electrode diffuses to the surface of the negative electrode. 100% is reduced in the negative electrode, there is no surplus oxygen around the negative electrode, and the hydrogen evolved in the negative electrode is a trace amount. If the float charge voltage is raised, or the ambient temperature rises, the charge current is increased, and the gas recombination efficiency becomes smaller as the charge current increases. The recombination rate is 90% at 0.05 C. When the current is at 0.1 C, the gas is at a rate of 0.1 C. The recombination efficiency is approximately zero. As shown in Fig. 1, at this time, the oxygen accumulated on the negative electrode and the hydrogen gas deposited on the surface of the negative electrode are many, the internal pressure of the battery is lifted, and the exhaust valve is opened, causing serious shortage of water in the battery. 2.5 temperature effects

When the battery is charged, its internal gas recombination itself is an exothermic reaction, which causes the battery temperature to rise, the float charge flow to increase, and the gassing amount to increase, which causes the battery temperature to rise higher. The battery itself is “lean liquid”, and the assembly is tight, and the interior is tight. It is difficult to dissipate heat. If the heat is not removed in time, the heat will be out of control. When the voltage at the end of the floating charge is too high and the ambient temperature around the battery rises, the thermal runaway of the battery will be intensified.

For every 1 °C increase in temperature, the battery voltage drops by about 3 mV/cell, causing the float current to rise and the temperature to rise further. Temperatures above 50 °C can deform the battery compartment.

When the temperature is lower than -40 °C, the valve-regulated lead-acid battery can work normally, but the battery capacity will decrease.

Valve-regulated lead-acid batteries have high temperature requirements due to structural problems. Everyone has noticed this. For this reason, temperature compensation measures are taken into account when designing charging equipment, but the selection of temperature sampling points is crucial, and it is directly related. The effect of compensation. There are three temperature sampling points, namely the air temperature near the battery, the surface temperature of the battery casing and the internal electrolyte temperature of the battery. The first is the easiest, and this method is basically used at present, but this method is very inaccurate, because the battery temperature rises for some reason, but the rise of the battery temperature is difficult to cause the temperature of the air near the battery to rise. Therefore, this kind of compensation measure is basically useless; the third part can best reflect the actual situation of the battery, but it is difficult to realize; the second part is the most practical and easy to implement. At present, the enterprise has designed the temperature compensation unit according to the sampling of the second place. 2.6 types

Valve-regulated lead-acid batteries are classified into three categories, namely, large, neutral, and small. The monomer is large at 200 Ah and above, medium-sized at 20-200 Ah, and small at 20 Ah or below.

Power systems are generally designed with large lead-acid batteries, while UPS power supplies are designed with medium-sized lead-acid batteries.

2.7 battery capacity

In the manufacturing process of the lead-acid battery plate, the green plate is charged, the lead on the positive electrode plate is turned into lead dioxide, and the lead on the negative electrode plate becomes spongy lead. But because of the plate in the factory

Characteristics, application and maintenance of valve-regulated lead-acid batteries

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Table 1 Watts of each battery discharged at a final voltage of 1.67V 151015202530354045601201803004806007201440

UXL33?1220817913110486.774.766.359.754.650.440.42316.410.87.36.15.32.7

44?1227723917513811699.688.479.672.867.253.830.721.814.49.88.173.6

55?1234729921917314512511199.5918467.338.427.31812.210.18.84.5

66?641636926320717314913311910910180.74632.821.614.612.110.55.5

88?655447835027621119917715014613410861.443.728.819.515.2147.6

110?669359843834528924922119918216813576.754.63624.420.217.59.1

165?274160150142236732629026424322619111684.955.837.530.526.213.6

220?298780166956348943438735232330225415411374.45040.634.918.1

330?21481120110038447336515805264864523812311701127560.952.327.1

550?224682002167114061222108596787981075363538628318612510287.245.2

1100?24937400333432813244411701933175716181506127077156637225020317490.4

1550?2740560055014421936663255290026362429225919051157849558375305262136

2200?29874800666865626488843403866351432383012254015421132744500406349181

3300?214811120091002984397332651057995271485745183810231316981116750609523523271

Time min

Battery model

W

The time is limited, it is impossible to convert all the substances into active substances. For this reason, the national standard stipulates that the new battery reaches 90% capacity, and only in the future daily use, the capacity gradually reaches the normal value. After 2 years of installation, Requires 100%.

China, Japan, Germany industrial batteries use a 10 hour rate, the United States industrial battery standard is 8 hours.

China's electricity, postal and telecommunications standards stipulate that the 10-hour rate battery has a capacity of 0.55C10 at 1 hour.

Japanese industrial standards stipulate 2V, 10 hour battery, 1 hour rate capacity is 0.65C10; 6V, 12V, 10 hour rate battery, 1 hour rate capacity is 0.6C10. 20 hour rate battery, 10 hour rate capacity is 0.93 C20, the capacity at 1 hour rate is 0.56C20.

The power system is generally designed to use a 10-hour lead-acid battery, while the UPS power supply is designed to use a 20-hour lead-acid battery.

2.8 life

Industrial batteries can be divided into two categories: one for deep cycle batteries and the other for "charged" batteries for float charging. The battery used for recycling uses the number of deep cycles to indicate its service life. The battery used for charging and discharging at a depth of 0.8C10 has a life of more than 1200 times. The battery used for floating charge can reach 10 to 12 years, and some can reach 15 to 20 years. The battery is considered to have an end of life when it has only 80% capacity.

3 valve-controlled lead-acid battery application

3.1 UPS battery selection

For example, the power output of a UPS is 50kVA,

DC voltage range is 330~480V;

Discharge time 30min;

The cell termination voltage is 1.67V;

UPS efficiency is 0.90;

The power factor is 0.95.

Calculation and selection

1) Convert the kVA number of the UPS to kW

50/(0.9×0.95)=58.48kW

2) Determine the number of batteries required n

n=330V/1.67V=198

3) Make sure the battery voltage does not exceed the DC voltage range

198×2.27=449.46V<480V

4) Determine the power per unit

58480W/198=295.35W

Since the condition for ending the service life of the battery is 80% of the discharge capacity of the battery, the capacity at this time should be used as the condition for the first selection.

295.35W/0.8=369.19W

5) Find the appropriate termination voltage (1.67V) discharge time (30min) from the power data of the YUASA specification.

From Table 1, find out that the model UXL220-2 can withstand 387W>369.19W and has a design life of 15 years.

3.2 Selection of power system battery

For example, a 220kV substation 220V DC load is

Frequent load 16.0A;

Accident lighting 18.2A;

Communication power supply 9.1A;

Table 2 GFM type battery different time discharge rate and different discharge termination voltage capacity conversion coefficient and capacity coefficient table termination voltage V capacity conversion coefficient capacity coefficient different discharge time (min) Kc and Kcc

1/121293059608990120150180240300360390420479480

1.75Kc1.541.531.000.9840.6200.6150.4820.4790.3870.3370.2890.2340.1950.1690.1610.1530.1360.135

Kcc0.4920.6150.7190.7740.8430.8670.9360.9751.0141.0471.0711.080

1.80Kc1.451.430.920.9000.6000.5980.4760.4720.3740.3240.2800.2240.1900.1660.1580.1500.1320.132

Kcc0.4500.5980.7080.7480.8100.8400.8960.9500.9961.0271.0501.056

1.83Kc1.381.330.8430.8230.5700.5650.4580.4550.3570.3160.2700.2170.1840.1600.1530.1450.1270.127

Kcc0.4120.5650.6830.7140.7900.8100.8680.9200.9600.9951.0151.016

1.85Kc1.341.240.8000.7800.5580.5400.4320.4280.3440.3060.2620.2140.1800.1570.1480.1400.1230.123

Kcc0.3900.5400.6420.6880.7650.7860.8560.9000.9420.9430.9800.984

1.87Kc1.271.180.7640.7550.5480.5200.4130.4080.3340.2980.2580.2090.1770.1550.1460.1370.1200.120

Kcc0.3780.5200.6120.6680.7450.7740.8360.8850.9300.9490.9590.960

1.90Kc1.191.120.6850.6760.4950.4900.3830.3810.3210.2890.2530.2000.1700.1500.1400.1310.1180.118

Kcc0.3380.4900.5720.6420.7230.7590.8000.8500.9000.9100.9170.944

Capacity conversion factor Kc=I/C10(1/h) Capacity coefficient Kcc=Kc·h

Telecontrol power supply 4.5A;

Current statistics 47.8A;

1 hour capacity statistics 47.8Ah.

Calculation and selection

1) Determine the number of batteries based on the highest voltage n

n=1.05×rated voltage/floating voltage

=1.05×220/2.25

=102.67 take n=102

2) Battery discharge termination voltage UZ

UZ≥0.85×rated voltage/n

=0.85×220/102

=1.83V

3) Battery capacity selection CC

CC=KK×CS/KCC

= reliability coefficient × discharge capacity / capacity factor

=1.4×47.8/0.656

=102Ah

(The capacity factor can be found in Table 2).

Select the nominal capacity of the battery C10 = 200Ah.

Note: The reliability factor is 1.4, which has considered the effect of low temperature on the battery, the inconsistent effect of the battery parameters, and the end of life when the battery capacity is 80% lower. 4 use precautions

Valve-regulated sealed lead-acid batteries are also called "maintenance-free batteries". Due to their ease of use, they have been widely used in the power, post and telecommunications departments in recent years, but because they do not understand the characteristics of valve-regulated sealed lead-acid batteries, they often It was scrapped in a few years and caused great losses to the company.

It is a mistake to first treat the "maintenance-free battery" as maintenance-free. The "maintenance-free battery" is just the manufacturer's advertising language. Valve-regulated sealed lead-acid battery should pay attention to observe the temperature of the battery during use. Pay attention to the floating charge voltage at any time. If the charging device does not have the function of compensating for temperature, it should increase the temperature of each cell by 1 °C. Decrease by 3mV.

Since the inside of the valve-regulated sealed lead-acid battery is not observed, it should be periodically tested for discharge during use to detect the battery capacity and avoid the role of the backup power source due to the decrease in capacity. It should be noted that the battery should not be over-discharged during discharge. It must be recharged within 12 hours after discharge, otherwise it will cause permanent damage to the battery. Pay attention to the capacity of the valve-regulated sealed lead-acid battery and the type of battery. The same two sets of 100Ah220V Japanese soup shallow battery, the actual situation is: a group of 100Ah, 36 batteries, 10 hours rate 100Ah, 1 hour rate 60Ah, 15 years Lifespan; another group of 100Ah, 18 cells, 20 hours rate 100Ah, 1 hour rate 56Ah, 3 years life. It can be seen that there are differences in capacity and there are differences in lifespan. The difference in price is actually 4 to 5 times.

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