Foreword: (keyword: launching tower, UPS, back-up source battery, mobile communication) as the common civilian mobile communication, mobile phone has been the popular tool recently. No matter traditional 2G or recent 3G wireless communications expand microwave signal by signal tower, so signal tower becomes the infrastructure in city and countryside, which is convenient for living and working. People tend to rely on it.
I. The back-up source battery requirements of mobile communication microwave tower:
The signal tower is consisted by transmitting equipment, receiving equipment, antenna system, power apparatus and monitoring device assuring normal running of telecommunication line and unmanned maintenance. The power-supply device not only has AC direct feed signal tower, but also UPS back-up source drive system so as to prevent interruption of work by power cut. Earlier power source tends to use lead-acid battery as the power supply of back-up source. Because plumbic acid is not environmentally friendly and has other shortcomings of low energy density, large size, short cycle life, etc., nowadays, the new or rebuilding base stations gradually begin to apply lithium ion battery as he power supply of back-up source. Based on the above issues, our customers require to apply lithium ion battery as major power supply, so that the back-up source system can support the transmission system for over two hours after power cut and meet the requirement of long-term field work.
According to the power consumption and transfer efficiency of customers’ transmission system, we calculate that the battery pack only needs 48V 65Ah current to meet the customer’s requirement of working hour. In order to assure the stability of the whole system, we apply Japan lithium ion cell which has high consistency and built-in multi-protection, including explosion-proof valve, PTC, etc. because the battery pack has high voltage, large capacity and high ambient temperature.
PCM protective system unit of power-supply system contains: 1. set up overcharging and over-discharging protection of single battery; 2. Temperature protection of the whole battery pack, including overcurrent and short circuit; 3. balanced system between single battery.
The test of battery capacity consists of detection system and display system. The test calculated by current and voltage, has precise display and measurement and displays the charging and discharging status of the battery with LCD display screen by dynamic visual image.
II. Back-up source battery design solution of mobile communication microwave tower
1）Design parameters of battery pack: Customers require that the battery ought to work for two hours under 1000W AC power supply system. In accordance with the transfer efficiency and voltage of UPS, we can calculate that the voltage of the battery is 48.1V, and its capacity is 65Ah, which can support the system work for 150 minutes under full load.
2）Design parameters of PCM: Single battery has protection function of overcharging, over-discharging, temperature, overcurrent, short circuit, etc. The certain parameters are as follow:
• Over-charged protection voltage of single battery: 4.22±0.25V
• Over-charged recovery voltage of single battery: 4.15±0.50V
• Over-discharged protection voltage of single battery: 3.00±0.10V
• Over-discharged recovery voltage of single battery: 3.30±0.10V
• Over-discharge cut-off current of battery pack (10ms): 70A
• Balanced current of charging: 50±10mA
• Balanced voltage of charging: 4.18±25mV
• Temperature protective range of battery (restorable): -20~60℃
• The finished product has protective function of short circuit.
3）The design functions of battery capacity monitoring system: It applies intelligent dedicated chip and LCD display screen, which can set up the parameters by keypad at any time. The display parts contain current capacity, current capacity percentage, current voltage, charging current, discharging current, remaining time of discharging, RSOC and ASOC.
4）Design requirement of battery whole construction: The basic station has wide distribution and is put in field. Considering insulation, damp-proof and anti-aging deterioration of the battery, the housing structure mainly applies fiberglass sheet. Besides, there are so many battery packs, we utilize engineering plastics stent for battery to fix and separate the battery pack so as to solve the issues of isolation and heat dissipation.
5）Secondary protection: Set a fuse preventing abnormal overcurrent short circuit for the whole battery pack, in order to avoid overcurrent led by non-performing batteries and malfunction of guard plate. It will produce overcurrent after PCM system failure, and then the fuse will cut off the output circuit of the whole battery pack, which is unrecoverable.
6）Lithium ion cell: 18650 lithium ion battery (parameters of single battery:18650/2500mAh/3.7V) applies Japan imported original cell. Therefore, it has good safety performance and consistency so as to assure the reliability of the whole battery pack.
III. Back-up source battery design block chart of mobile communication microwave tower