Wiring diagram 123SmartBMS

After the introduction of affordable LiFePO4 batteries, off-grid solutions became feasible. It is vital that such batteries are charged very carefully. In other words, they can easily be over-charged, or over-discharged. Cell-temperature and current are also very important, in order to guarantee a long life.

The 123smartbms Battery Management System (or: BMS) is primarily intended for prismatic LiFePO4-cells, but can also be adapted by the end-user for other cells like Li-Ion and LiPo, provided the cell-voltage is in the range of 2V to 5V.

The diagram shown on  the right, gives a nice overview of a wired system consisting of a single pack of batteries with BMS-boards and the current-sensors.


For a single pack of 4 batteries, the system would consist of:

1 BMS-'IN'-board

1 BMS-'OUT'-board

2 Ordinary BMS-boards

2 Current sensor


To measure current during charging and dis-charging, the current sensor should be connected in the position indicated. This is important, as this sensor is used for the so-called Coulomb-counting software, with which the BMS-controller calculates the remaining battery-capacity.


 In the settings-area of the Bluetooth App, one can customise practically anything:

- Battery-capacity: 0.1 - 999 kWh.

- Cell-voltages (Vmax, Vmin, Vbypass & V-recharge)

- Cell-temperature (Tmax, Tmin in degrees Celsius)