Principles of selecting a BMS for a battery pack

Here are some simple rules to help you choose the right BMS for the package you are designing.

• Type of cells. Due to the different operating range voltages for different cells, it is necessary to choose a BMS designed for the correct cell type. For example, a BMS for LiFePO4 cells will protect an operating range between 2.5 and 3.65V per cell, while one designed for LI-Ion cells will protect 2.7 to 4.25V. It is not possible to use them interchangeably.
• Number of cells in the package. Each BMS is adapted to the specific number of cells it supports. This information is given in the BMS symbol.

• Type of BMS. Plain or SMART.
  • The traditional BMS does not require any maintenance during the operation of the package. All the safety parameters are set in it at the factory, and it is practically “invisible” to us when connected. Its additional advantages are smaller size and weight, much lower resting current consumption – important if you anticipate longer battery storage periods, and, of course, a lower price. In the case of the BMS DALY, an additional advantage is total water and dust resistance.
  • BMS SMART- enables full monitoring of the built package. Virtually all parameters for the entire battery and individual cells are immediately available. Depending on the communication method and the software used, it is also possible to partially change them. BMS SMART, depending on the version, can work with mobile devices (Bluetooth), LCD touch screens, voltage indicators, PCs and other external devices. Their disadvantages are larger size, more complicated operation (if you want to use additional functions) and higher resting current consumption. For this reason, they are not recommended for packs with a capacity of less than 10Ah. All batteries equipped with BMS SMART should be periodically recharged during storage. Due to the presence of multiple connection slots, it is not possible to achieve the same degree of moisture protection as for ordinary BMS.

When choosing a SMART BMS, it is worth considering right away how we will monitor the data coming from it. If we only want to use the mobile app, it doesn’t matter much. All BMS of this type allow communication over BT.

Also, the LCD touch screen fits all SMART Daly BMS as an alternative to BT. The use of a battery level indicator already requires the existence of an LED 12 connector, and communication over UART, RS 485 or CAN a proper communication connector.

• If you plan to connect batteries equipped with a BMS in parallel, the problem is much more complicated and requires the use of special BMS, further supplemented by a “parallel module.” This topic is discussed in detail here.