Application of Telecom-grade 12V Battery in Access Network

0 Introduction

Looking at the development of 12V batteries for access networks in China, 2000 was a watershed year. Two things that happened in this year are worth reviewing again: First, the access network-battery research team of the former Huawei Electric proposed the concept of telecom-grade 12V batteries for the first time and developed a new generation of access network supporting batteries (i.e., the current Emerson Telion series of telecom-grade 12V batteries) based on extensive investigation and research; another important event was that the former Hebei Telecom, faced with the high failure rate of 12V batteries for access networks (UPS type batteries), took the initiative to select batteries for access networks, changing the original situation where the batteries were selected by the access network OEM supplier alone, greatly improving the quality of network operation. However, an interesting coincidence is that the former Hebei Telecom chose the telecom-grade 12V batteries of the former Huawei Electric, and both were renamed Emerson Network Power at the end of 2001, one due to the split of North and South Telecoms, and the other due to joining Emerson Electric.

The status of the access network supporting batteries can be summarized as follows:

- In terms of usage conditions, there are large differences between rural and urban areas (including grid conditions and ambient temperature);

——In terms of product variety, in areas where no selection is made, product quality varies greatly;

——In terms of usage, UPS products have a high failure rate, which has become one of the hidden dangers affecting the stable operation of the network;

——In terms of upgraded products, telecom-grade 12V batteries that meet the requirements of access networks have performed well.

1 Access network supporting 12V battery

1.1 Service life

The battery design life provided by battery manufacturers is a theoretical value under specific conditions and cannot be equated with the actual service life. The actual service life is closely related to the use conditions (ambient temperature, discharge depth, power outage frequency, battery management, etc.), and there is a certain difference from the design life, or even a big difference. Table 1 shows the statistical results of the service life of UPS type 12V 100A·h batteries put into operation during the same period (with 80% of the rated capacity of the battery as the end of life mark). It can be seen that the proportion of batteries with a service life of less than one year accounts for 30%, the proportion of batteries with a service life of less than two years is as high as 58%, and the proportion of batteries with a service life of more than two years accounts for only 12%.

Table 1 Statistics of access network battery service life

Run time	Less than one year	More than one year but less than two years	More than two years
Proportion	30%	58%	12%

Accordingly, the cumulative failure rate of telecom-grade 12V batteries from 2000 to May 2003 was 725ppm, a significant improvement over UPS-type batteries (which have a failure rate of more than 30% after two years of use).

1.2 Maintenance Survey

At present, most of the 12V batteries supporting the access network are built into the bottom layer of the main equipment cabinet. The inspection of the battery is sometimes neglected in daily access network maintenance. Table 2 shows the maintenance of the built-in batteries of the access network obtained through inquiry and investigation. It can be seen that users are not only very familiar with the battery maintenance methods, but also have rich experience. However, there are still some weak links in the configuration of access network battery maintenance personnel and maintenance implementation. Currently, only 23% of them can maintain themselves, and nearly 80% cannot be taken care of.

Table 2 Survey on maintenance of storage batteries supporting access network

Do you know how to maintain the battery?
Condition	Very well understood	Better understanding	Don't understand
Proportion	54%	46%	0%
Can the battery be maintained normally?
Condition	Capable and maintainable	Capable but unwilling to maintain	Capable but not maintainable	No ability to maintain
Proportion	twenty three%	38%	39%	0%

From the perspective of battery maintenance, the following factors need to be taken into consideration when selecting batteries:

——Battery performance-price ratio: In areas where the use environment is not ideal and the transportation location is relatively remote, equipment reliability (quality performance) is the primary consideration, and price factors are secondary (within a reasonable battery performance-price ratio range);

——The selection of 12V battery should be based on the actual use requirements of the access network and in accordance with the YD/T799-2002 standard to formulate the corresponding selection specifications for batteries;

——Main and auxiliary equipment bundled (integrated) matching mode. Due to the decentralized construction of access networks, the workload of engineering installation and maintenance is large, and some equipment has built-in batteries. In general, the integration of main and auxiliary equipment should be the preferred solution;

——Optimize 12V battery configuration From the perspective of battery configuration design for overseas key-return projects, it is a mainstream trend to divide the design capacity into two, which can improve the power supply safety of the system. For example, 48V 200A·h, using two groups of 48V 100A·h in parallel, is more reliable than one group of 48V 200A·h.

2 Optimized design

The design indicators of Emerson's batteries used for access network support comply with YD/T799-2002 and are generally recognized by users.

2.1 Capacity Design

The first discharge can reach 100% of the rated capacity.

Under specified conditions, the rated capacity of a battery refers to the A·h capacity indicated by the manufacturer that can be provided after full charge. Among them, _{C10 is} the 10h rate rated capacity A·h; C3 is the 3h rate rated capacity A·h, the value is 0.75 C10 ; C1 is _the 1h rate rated capacity A·h, the value _{is 0.55} C10 .

Emerson batteries are designed with sufficient capacity and can pass strict capacity tests by users. However, general-purpose UPS batteries (such as high-power design types) mainly have the advantage of constant power discharge (12V 100A·h 15min rate is 370W), and it is often difficult to meet the requirements when using the YD/T799-2002 method for acceptance.

2.2 Active material design

The positive active material of lead-acid batteries is lead dioxide, and the negative active material is sponge lead. The reduction in the utilization rate of active materials can effectively extend the battery life, but relatively increase the total weight of the battery. The weight of Emerson batteries (T12V100SE/A, T12V100SE/B) is about 42kg, which fully meets the requirements of Article 5.6.2 of YD/T799-2002.

2.3 Deep discharge recovery index design

The batteries used in access networks are often used for low current and long-term deep discharge. Deep discharge of batteries is often difficult to avoid. Emerson batteries improve the deep discharge recovery ability of batteries through the following improved designs:

——Increase the Sn content of the grid alloy to reduce the formation of the inert layer between the grid and the lead paste and improve the charging efficiency;

-- Improve the grid structure, adopt a staggered grid structure (radial structure is better for high-power batteries), and increase the thickness of the battery plate (to improve the stress resistance, prevent grid deformation, reduce lead paste softening and loosening, and enhance the corrosion resistance of the grid);

——The lead paste is reshaped to extend the passivation time of the lead paste, making it suitable for long-term discharge.

2.4 Built-in air collection and exhaust design

The gas collection and exhaust device used for access network equipment has been recognized by more and more users. It can collect and neutralize the gas (hydrogen mixed gas and trace acid mist) generated during the battery charging process and discharge it outside the equipment, effectively avoiding serious accidents such as explosion and corrosion.

2.5 Comprehensive comparison

See Table 3 for details.

Table 3 Comparison between Emerson's telecom-grade batteries and typical UPS-grade batteries

project	UPS Grade Batteries 12V 100A·h	Emerson Telecom Grade Battery 12V 100A·h	illustrate
Design life/year	≥8	≥12	Telecom-grade batteries with higher reliability
C 10 capacity/A·h	93* ( C 20 is 100)	>105	Communication standard ≥100
Weight/kg	≈33	≈42 (internal); 54 (external)	The material composition of telecom-grade 12V batteries is similar to that of 2V batteries
Grid Alloy	Ordinary low tin	Low calcium and high tin	High tin materials are good for deep discharge recovery and corrosion resistance, but the cost is relatively high
Grid thickness/mm	+2.65	+4.2	Thick plates improve the battery's ability to withstand deep discharge stress deformation and corrosion
Shell material	PP/Ordinary ABS	ABS/high strength, V0 flame retardant grade	Flame retardant for built-in equipment applications
Pole seal	One layer of adhesive seal	Three-layer sealing	Key technologies to solve battery leakage
Deep discharge short circuit recovery	≈60%	≈90%	Key indicators of communication applications
Gas collecting and exhaust device	none	have	When the device is used inside, the main device must be protected from acid mist corrosion

* Note: If the UPS type battery (battery size is relatively small) is required to be designed to C10 to reach 100A·h, the battery needs to be designed with a relatively tight assembly, the battery grid needs to be thinned, and the utilization rate of active materials needs to be improved, which will reduce the battery life to a certain extent. In addition, _a too tight assembly structure will reduce the volume of electrolyte, and the probability of thermal runaway caused by high temperature water loss of the battery may increase.

3 Application

3.1 Sampling Survey Description

In order to understand the use of Emerson's telecom-grade 12 V 100 A·h batteries in access network support, we selected areas with representative grid conditions and ambient temperatures for sampling tests.

3.2 Survey on battery usage at access points in Sui County

There are 30 points in Sui County that use Emerson batteries. Six points were randomly sampled in this survey, of which five points directly disconnected the AC power and used batteries to power the load. The load working current was about 3 A. The average battery voltage was 51.02 V at the beginning of discharge, and the average voltage was 48.24 V when the discharge was stopped manually. The voltage consistency of the single battery was good during the discharge process, and the average discharge time was about 20 h. Another point used 3 h rate discharge with a discharge current of 25 A. After 3 h of discharge, the battery voltage was 46.1 V, and the result was very ideal (3 h rate capacity standard: when the current is 0.25 C ₁₀ and the discharge current reaches the termination voltage of 43.2 V, the discharge time is ≥ 3 h).

The sampling test results meet the application requirements.

3.3 Investigation on battery usage in Fuping County

A group of 48V 200A·h batteries (consisting of two groups of 12V 100A·h connected in parallel) were randomly checked. They were put into operation in late December 2000. The discharge rate was 1h, the discharge current was 110A, and the discharge lasted for 1h. The battery group voltage was 45.2V and the capacity was qualified.

The sampling test results meet the application requirements.

3.4 Investigation on battery usage in Yongqing County

A group of 48V 200A·h batteries (composed of two groups of 12V 100A·h connected in parallel) were randomly checked. The battery pack voltage was 43.94V and the capacity was qualified when the discharge rate was 3h and the discharge current was 50A for 3h.

The sampling test results meet the application requirements.

4 Conclusion

The 12V battery for access network should preferably be telecom-grade 12V battery, and UPS-type battery should be used as little as possible. The actual operation experience in the past few years shows that the actual use of telecom-grade 12V battery that meets the YD/T799-2002 standard in access network is significantly better than that of UPS-type battery.