Video: BVS – Technical guide

Video transcript

How the BVS is installed on a battery bank, in what order it is wired, how the modules are addressed and how a monitoring test is set up and checked. A battery bank is dangerous even with nothing switched on. Insulated tools, eye and face protection, acid-resistant gloves and apron, water for rinsing, and no jewellery. No flames or sparks near the cells, and the ventilation working. To site go the control unit with its cables and the PC software, one module per cell with its fused sense cables and a short bus cable,

a longer cable to the first module, and the temperature sensors. String modules and the current clamp are optional. On the front of the control unit: the 3 status lamps, the memory card slot and the 4 temperature inputs. Power is lit whenever it is on. Status is steady when idle and flashes during a test. Alarm flashes when a cell, or the whole string, reaches its critical value. On the back: the mains inlet and switch, the bus socket that goes

to the first module, and the USB port for the PC. The unit accepts 90 to 264 volts, and feeds every module on the bus at 66 volts. The cell module is small and has only what it needs: the two voltage sense terminals, rated 30 volts, a red LED, the SET button used to give it its address, and two bus sockets, IN and OUT. The sense cables cannot short a cell: the banana plugs carry extra insulation, and each cable has a fuse inside the yellow sleeve, as I triple E 14 91 asks.

The yellow end goes to the battery. The rule: connect to the module first, then the battery; disconnect the battery end first. The installation follows one sequence, with the control unit switched off and unplugged. Clean the spot on the cell and fix the module. Bus cable into its IN socket, OUT to the next module. Sense leads to the module, then the clips to the cell.

Repeat along the string, and only then power up. Here are the first two cells. The bus cable from the control unit goes into the IN socket of the module on cell one. From its OUT socket, a short cable to the IN of the next module, and so on down the string. Then each module gets its sense leads: black to the minus of its own cell, red to the plus. Along a string the pattern simply repeats.

The bus runs from module to module, and each module measures only its own cell. Up to 128 modules on one control unit. If one module fails, the bus still reaches the rest. This is why the order of the bus matters. The plus potential of cell one, point A, travels through the bus cable to module two. Module two has its minus lead on point B, the minus of cell two, so it measures the voltage across the link between A and B.

Each module measures the link before its cell. Cell number one can be at the main minus or the main plus of the bank. The wiring does not change. What changes is the order in which the modules are addressed, so that module number one is always on cell number one, and every result carries the right cell number. In the PC software: connect over USB or Bluetooth and let it find the unit, enter the battery data and the number of cells, press Reset, then press SET on each module in cell order; its LED flashes once.

Choose the scan interval and the nominal cell voltage, and start. And the complete test. The bus runs from the control unit along every row of cells, a temperature sensor measures the ambient air, and the discharge unit is connected across the string. The PC talks to the control unit by USB or Bluetooth, and the discharge and the cell data are recorded side by side. During the test the scan settings can be changed without stopping: the interval, and whether inter-cell voltage or temperature is recorded. A module with a communication fault is drawn dashed and reported in the status

messages, and a cell removed from the string can be taken out of the monitoring. If a reading looks wrong, check the module against a stable source and a reference voltmeter. At 12 volts, for example, it must read between 11.958 and 12.042. The millivolt channel is checked with a second module in front of the first. Maintenance is mostly about the battery around it. Keep the modules free of electrolyte, take them off before topping up water or opening links, refit every link before putting them back,

and never unplug a bus cable while the system runs. Battery maintenance, from Amperis.