Battery Applications in Harsh Environments and Solutions

Problems Faced by Batteries in Harsh Application Environments

With the increase in outdoor base station applications, battery failures in harsh environments have gradually become more prominent. In regions like Pakistan and India in South Asia, this has led to economic losses for operators and harmed customer satisfaction. To address the large-scale battery failures in such harsh environments, ZTE Corporation has conducted extensive research to deeply understand the application scenarios of batteries and analyze the causes of battery failures. The key issue does not lie with the battery itself but with the outdoor battery cabinets not providing sufficient high-temperature protection for the batteries. To fundamentally solve the problem, a comprehensive solution for outdoor battery applications in harsh environments must be provided.

Comparison of Active Heat Dissipation Technologies for Outdoor Battery Cabinets

There are various cooling methods for outdoor cabinets. Which cooling method is suitable for outdoor battery cabinets? This depends on the product characteristics of the batteries. For lead-acid batteries in communication DC power systems, the most important factor for users is the battery’s lifespan. The main factors influencing the lifespan of lead-acid batteries are environmental temperature and grid conditions.

The lifespan of lead-acid batteries is closely related to environmental temperature. The higher the ambient temperature, the shorter the battery’s lifespan. When the environmental temperature exceeds the battery’s designed lifespan temperature (25°C), the lifespan is halved for every 10°C increase.

The number of discharge cycles and the depth of discharge directly affect the battery’s lifespan. The more frequent the discharges and the deeper the discharges, the shorter the battery’s lifespan. In other words, frequent power outages reduce the battery’s lifespan.

For outdoor base stations, operators are often unable to improve grid conditions, or the cost of improving the grid is too high to bear. Therefore, the approach of reducing the working temperature of the battery environment is adopted to extend the battery’s lifespan.

Traditional Cooling Methods for Outdoor Cabinets

The traditional cooling methods for outdoor cabinets include fan ventilation or heat exchangers. However, these methods cannot lower the internal temperature of the cabinet below the ambient temperature outside. In high-temperature areas (generally above 40°C), active cooling is needed to ensure that the internal temperature of the outdoor battery cabinet is lower than the external environmental temperature. ZTE has innovated by integrating refrigeration components into the outdoor battery cabinets.

Communication main equipment (such as GSM, transmission, etc.) and DC power system components (rectifiers) generate heat during operation, but batteries behave differently. According to the electrochemical mechanism of battery charging and discharging, batteries do not generate heat during discharge. During normal charging (without overcharging), they also generate minimal heat. Therefore, the heat generated by the battery during normal operation can be ignored. Thus, outdoor battery cabinets do not have a significant heat source, and the required refrigeration capacity is low. Typically, outdoor battery cabinets require only 200–400W of refrigeration capacity.

Thermoelectric Cooling (TEC) Air Conditioning

Thermoelectric cooling (TEC) uses emerging semiconductor refrigeration technology and has many advantages for outdoor battery cabinet applications compared to traditional compressor-based air conditioning:

Simple structure and high reliability: The entire cooler is made up of a thermoelectric cooling module and connected wires, without the need for compressors or mechanical rotating parts, resulting in no vibration, friction, or noise. It has high reliability and a long lifespan (over 100,000 hours at 32°C).
Cooling unaffected by AC power outages: Powered by DC 48V, during an AC power outage, the TEC air conditioner continues to be powered by the battery, ensuring that cooling can still be achieved in the outdoor battery cabinet.
Cooling efficiency and capacity: While thermoelectric cooling may not be as efficient as vapor-compression cooling in high-capacity applications, the efficiency of vapor-compression cooling decreases as capacity reduces. TEC efficiency is not dependent on the size of the cooling load, making it ideal for applications with low cooling demand, such as outdoor battery cabinets.
Compact size: Particularly suitable for outdoor cabinet installations.
Cost-effective: Based on the above analysis, TEC air conditioning offers a high cost-performance ratio for outdoor battery cabinets.
Ease of maintenance: TEC air conditioners do not require refrigerant cycles, and without rotating compressors, maintenance is minimal. Regularly ensuring the insect-proof net is clear is sufficient.
Environmentally friendly: TEC air conditioners do not use refrigerants like Freon, which are harmful to the ozone layer, making them green and environmentally friendly.
TEC-Based Outdoor Battery Cabinets with Excellent High-Temperature Protection

The TEC outdoor battery cabinet consists of a TEC air conditioner, cabinet body, and thermal insulation layer. To meet the needs of installing different capacities and types of batteries, ZTE has designed a series of TEC battery cabinets. Two typical cabinets are shown in the figure: the left cabinet can install up to two sets of slim 12V 150Ah AGM or gel batteries, while the right cabinet can install up to six sets of slim 12V 150Ah AGM or gel batteries (or three sets of wide 12V 150Ah or 200Ah gel batteries). To achieve ideal cooling performance, the cabinet must have good insulation. The insulation material has been professionally designed to minimize holes and cuts, with a thickness of 40mm. Like the TEC module, the insulation is designed with an IP55 protection rating.

The TEC battery cabinets are designed with both cooling efficiency and product reliability in mind, selecting advanced cooling chips, high-reliability fans, and high-quality insulation materials. These TEC battery cabinets provide excellent high-temperature protection.