How to use BMS - Battery Management Boards

How to use BMS - Battery Management Boards 

General notes for BMS  

• Balancer bord will not perform any charging characterized process. (there won't be CC or CV charging process handled by balancer or BMS board) 
• Therefore a separate charger module or charger circuit should be used. 
• Do not connect the power adapter directly to your battery pack through a BMS board. It won't charge the battery pack in the way it should be done. Therefore, Batteries could explode or catch fire. 

BMS board may have the following options (some may not) 

• Over-discharge current protection though a shunt resistor(max current limit is specified) 
• Overcharge protection 4.2V/8.4V/12V 
• Over discharger protection 2.8V/5.6V/7.4V 
• Each cell Balancing  
• Temperature monitoring of battery pack 
• Bluetooth enabled BMS 
• Inbuilt Host communication RS485/CAN/I2C/UART 

Balancing required to make sure batteries are charged with their full capacity 

How a balancing board work 

• Check this link 
• Balancing can be used when you have multiple cells and charge all batteries to their maximum capacity 

Why some batteries charge faster or increase voltage faster? 

• The battery is low in quality or a weak battery – this will lead to quick voltage rise/ if let it rise without balancing battery heat up and explode  
• Due to the slight difference in the internal resistance of the battery compared to other batteries, one may charge quickly or its voltage increase faster 

In 2nd case balancing circuit in BMS comes handy, 

• It will balance raised the voltage by discharging using a small load resistor and a transistor circuit in the board.  

• E.g. – if a battery has voltage rise to 4.26V > 4.2V (standard) --> transistor will open path to load resistor so that the voltage of the battery will reduce to 4.2V from 4.25V 

 

Extra Example setup  

• Wall adapter 230V AC to 18V DC 6A --> charger module CC-CV 16.8V --> 4S BMS --> Battery pack  
• If you want to use a battery pack and while charging a changeover IC shall be used. With changeover IC, while charging, current to the load will be taken from the wall adapter. Do not take power from the battery while charging. This will overrun the charger.... charger will heat up and burn up while trying to supply the power to load and to the battery pack charging  
• With the above setup, you can leave battery charging... once it reaches the max voltage BMS board will cut off the power to the battery pack  
• If you making a backup power for some device a power path controller IC shall be used.