LFP BMS CELL MODULE INSTALLATION Start with a LFP battery pack. Cells should be strapped or tightly packed so they cannot swell and deform.
Clean the terminals with some steel wool or emery paper to remove the oxide coating.
Start laying cell modules on top of cell interconnectors, bolts should be done up finger tight until a row is complete. Leave out the link at the end of each row till the end. When a cell module is correctly mounted the green LED will glow to indicate that the cell is in its safe voltage range.
Use bolts with spring washers and flat washers as shown. Stainless steel, galvanized or brass bolts and washers should be used.
Lay out and bolt down all the cell modules and interconnectors.
Tighten bolts with a spanner or wrench. Note the insulation on the handle, this can prevent accidental short circuits which can be very dangerous. Leave out the interconnect joining the ends of two rows until everything else is completed. Torque settings according to manufacturers specifications. As a general rule the bolt should be tight enough that the spring washer is flat. Take care not to over tighten.
This is an example of correct alignment of a cell module.
This is an example of incorrect alignment of a cell module. Note the uneven height resulting in distortion of the module.
Where terminals are to be connected a terminal post should be made from a 40mm length of threaded rod. Stainless steel is shown but brass can also be used.
An example of correct cable termination. If signal wires are to be used do not connect cables until signal wires have been installed.
An example of incorrect cable termination. Termination in this way can result in cell module internal electrical damage when the bolt is removed.
There are two signal solder pads on each module. Small signal wire should be used for connecting cell modules together. A wire stripping tool is very handy for this.
Daisy chain the modules together as shown. Solder each in turn. Signal outputs are isolated from the cell terminals and are non-polarized. For convenience the daisy chain should follow the cell interconnector chain. Do not connect signal wires to any cell terminal or cell module damage will result. The end result will be two wires at the ends of the daisy chain. Signal outputs can be used to control loads/chargers directly or be connected to a master control unit.
Check the resistance of the signal line. If all the cells are ok it should record about 0.75 Ohms per cell. A very high resistance or open circuit indicates a problem either with a cell or with a cell module. Do not allow the signal wires to contact the battery terminals.
The end result should look something like this.
Closeup of the cell module connections.
At the end of a row of cells the signal wire can be looped though the hole in the cell module for added strength. A 100mA quick blow inline fuse in the signal wire at the end of each row is also recommended.
When all of the cell modules have been connected and tested the solder joints should be covered with glue. This prevents moisture and dust causing current leakage problems from the cell terminals.
There are two LEDs on each cell module. The green LED is normally on if the cell is within its safe operating voltage. The red LED glows only when the cell reaches it fully charged voltage of 3.6V and is beginning to bypass some charge current.
An example of a cell bypassing.