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Telecom VRLA Battery Management Systems

Existing Telecom Base Station sites contain VRLA type batteries for energy backup. 4 units of 12V VRLA batteries serially connected to make 48V battery groups and these 3 or 6 groups (12 or 24 units of batteries are used) are parallel connected by that way the required energy capacity can be obtained.

Although it is expected that each parallel connected battery groups can take same amount of current during charge, due to the production differences and also the aging reasons battery groups do not take same amount of current in practice. When the cycle counts increase, batteries cannot be charged properly due to the internal resistance differences. During the discharge mode these unbalanced situation can age the battery groups and the expected capacity of such as 400Ah cannot be obtained from the batteries.  

Because of the wired parallel structure, any faulty battery can affect the battery group and also the total energy back up system.


Telco BMS uses the rectifier supplied current and voltage levels and take care of up to 16 units of 48V VRLA Battery groups. During the charge process, each battery voltage levels and group temperatures are monitored by the system.  Battery Control Unit (BCU) modules make current limitations, voltage and temperature monitoring and communicate through by using Mod-Bus like ASCII protocol to Main Process Controller (MPC) module.  MPC controls the all system and takes current limitation decisions and charge cut off decisions. At the same time MPC communicate with PC over USB 2.0 or Ethernet ports, with site monitoring system over RS485 port and internal GSM/GPRS modem daughterboard by separate serial interfaces. Each battery group is controlled by one BCU modules. Current and voltage control in BCU modules; prevent overcharge during charge process caused by the VRLA battery aging and asymmetric capacity.

Telco BMS can “balance” 12V battery voltage in the groups. ABC (Active Balancing Circuit) hardware in BCU can inject 1-2A balancing charge current to selected 12V battery. When the active balancing applied onto lower voltage batteries after the charge, all battery voltages in the group can be balanced for a while. This method fixes battery «top» voltages to preferred voltage level and cycling can be done from this point with the help of overdischarge control at the bottom.

Telco BMS

Telco BMS has  "19" Rack" type and “Modular” type models.  19" Rack model has maximum 5 battery group connection. Modular design permits upto 16 battery group and flexibility to add or remove battery groups by only adding a BCU module

MPC (Main Process Control) unit

MPC has 2x16 ch. LCD display and 4 button menu system is used for Human Machine Interface (HMI) on the front panel. RJ45 Ethernet, RS485 and USB interfaces are located at the rear panel of the MPC

BCU (Battery Control Unit)

BCU boxes has Communication BUS and battery voltage/temperature measurement probe connector on the front panels. Metric 8 (20 mm cable lug compatible) barrier type DSTB connector located at rear panel. Rectifier (-) and battery group (-) poles are connected to this power connector. 

Telco BMS VRLA-Lithium Hybrid Operation

Lithium battery packs are started to be used in Telecom applications within 2 years. But higher cost of Lithium batteries prevent full replacement of VRLA with Lithium. Telco BMS system allows VRLA and Lithium Hybrid operation. One or more group of Lithium-Ion Battery (Lithium Iron Phosphate-LFP, Lithium Manganese Oxide-LMO, Lithium Cobalt Oxide-LCO, Lithium Nickel-Cobalt Oxide-NCA etc.) can also be connected to Telco BMS BCU module. If one group is Lithium and the remaining groups are VRLA batteries, Lithium can be charged with 25A current quickly.  If faster charging required 2 BCU modules of Telco BMS can be parallel charge Lithium with upto 50 A. 

During the electricity cut off, firstly Lithium Battery is discharged. When the lithium battery is fully discharged, VRLA groups started to be discharged. This control algorithm controlled by Telco BMS’s MPC Module. With this hybrid operation, when the electricity cut off bellow approximately 2 hours, VRLA batteries don’t be cycled and the VRLA batteries operation life will get increased.

VRLA-Lithium Hybrid

Telco BMS system analyze all battery asset voltage, current and temperature and use specific algorithms to calculate state of charge (SoC) and state of health (SoH) of each battery. MPC module can report these information to Operation & Maintenance Center (OMC) via Ethernet TCP/IP connection. An optional GSM/GPRS daughterboard also be placed into MPC module to Access OMC via wireless network. 

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