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Battery Cell Voltage Monitoring

Cell Voltage Monitoring with BVS

Cell voltage monitoring during the capacity test is crucial for a complete capacity test. It enables identifying failing cells and replacing them, increasing our battery’s service life.

DV Power’s battery voltage supervisors are accurate battery voltage monitoring systems that monitor the state of health of battery systems. They record important battery parameters such as battery voltage, inter-cell connection voltage, and ambient temperature, acting as a support tool for capacity testing.

The system consists of a Control Unit (which can also be incorporated in the BLU-C series devices) and modules which are mounted on battery cells. These modules monitor cell voltage during the capacity test. An illustration of the battery voltage supervisor BVS connection to a battery string is shown in Figure 1. This solution requires the user to use one module per cell.

BVS Connection Diagram
Figure 1 – BVS connection to a battery with 6 cells

Cell Voltage Monitoring with BVS-4

In order to reduce the number of required modules and connections that need to be made, a new solution Battery Voltage Supervisor BVS-4 has been developed.

The newly released BVS-4 system consists of Cell Voltage Modules CVM-4 which can monitor the voltage of up to 4 cells. This significantly reduces the number of required modules. The number of connection cables to the battery is also reduced, thereby reducing the total setup time.

BVS-4 cell voltage modules have a voltage measurement range of 30 V per channel. Each module is also equipped with one temperature channel which is used to measure cell temperature on one of the four cells.

The connection of BVS-4 to a battery string with 8 cells is shown in figure 2.

BVS-4 Connection Diagram
Figure 2 – BVS-4 connection to a battery with 8 cells

As shown in Figure 2, only two CVM-4 modules are required to connect to a string of 8 cells with BVS-4.

Each CVM-4 module is equipped with a voltage sense cable set, containing 5 wires. Each wire is marked with a corresponding number (from 1 to 5).

The procedure for connection of CVM-4 to the string as shown in Figure 2 is described below.

  1. The cable marked with No. 1 should be connected to the negative (-) terminal of the first cell in a group of four, as shown in Figure 2.
  2. The cable marked with No. 2 is connected to the next adjacent negative (-) terminal (for example, of cell No. 2 in Figure 2).
  3. The cable marked with No. 3 is connected to the next negative (-) terminal, after cell No. 2 (negative (-) terminal of cell No. 3 in Figure 2)
  4. The cable marked with No 4 is connected to the fourth negative (-) terminal in the row of the corresponding module CVM-4.
  5. The cable marked with No.5 (with a red connection clip) is connected to the positive (+) terminal of the fourth cell in the row of the corresponding module CVM-4 ((+) terminal of cell No. 4 in Figure 2).

This process is repeated for every CVM-4. This approach reduces the number of required modules and the number of connections to the battery.

With BVS the number of required modules was the same as the number of cells and the number of necessary connections is twice as big. With BVS-4 the number of modules needed for any battery, where the number of cells is N, can be calculated by dividing the number of cells with 4 and rounding up to the next whole number. Furthermore, the number of necessary connections can be calculated as 5 x N/4.

As an example, for a battery string with 60 cells, we have the following configurations for BVS and BVS-4:

System No. of modules No. of connections to battery No. of communication cables
BVS 60 120 60
BVS-4 15 75 15

Cell Temperature Measurement

Cell voltage modules CVM-4 are equipped with one temperature measurement channel, which can be used to measure cell temperature on one of the four cells the CVM-4 is connected to.

In order to measure the temperature, special voltage sense cables need to be used, that contains the temperature sensor within the VS cable set. The temperature sensor is mounted to the negative terminal of the cell via an M10 lug. The connection of BLU-C and BVS-4 to a battery with cell temperature measurement is illustrated in Figure 3

Cell Voltage Monitoring using BVS-4
Figure 3 – Connection of BLU-C and BVS-4 with temperature measurement to a battery string

Data acquired by the cell voltage monitoring modules is sent to the Control Unit and then to the DV-B Win software. The control unit can also be incorporated into the BLU-C series of devices, as shown in Figure 3. Together with DV Power’s Battery Load Unit, BVS-4 is an ideal tool for battery capacity testing.

February 27, 2020


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