How Does The BMS Equalize Battery Voltages When Connected In Parallel

A battery management system (BMS) is a device that monitors and controls the charging and discharging of a battery pack. It can also be used to equalize the voltages of the batteries in a pack before connecting them in parallel.

There are two ways that a BMS can equalize battery voltages:

• Active balancing: This is the most common method. The BMS uses a small amount of current to charge the cells that are lower in voltage than the others. This helps to bring all of the cells to the same voltage before they are connected in parallel.
• Passive balancing: This method relies on the natural self-discharge of the batteries. As the batteries discharge, the voltage of the cells that are lower in voltage will drop more quickly than the others. This will eventually bring all of the cells to the same voltage.

It is important to equalize the voltages of the batteries before connecting them in parallel. This is because if the batteries are not at the same voltage, the higher-voltage battery will try to force current into the lower-voltage battery. This can damage the lower-voltage battery and shorten its lifespan. 

Here are the steps on how a BMS equalizes battery voltages before connecting parallel:

1. The BMS first checks the voltage of each battery cell.
2. If any of the cells are lower in voltage than the others, the BMS will start to charge them.
3. The BMS will continue to charge the lower-voltage cells until they reach the same voltage as the others.
4. Once all of the cells are at the same voltage, the BMS will stop charging them.

It is important to note that: The BMS will only equalize the voltages of the batteries if they are connected to the BMS. If the batteries are not connected to the BMS, the voltages of the batteries will not be equalized. If the BMS's are out of sync, Batteries connected in parallel will not be equalized.

Here are some tips for equalizing battery voltages before connecting parallel:

• Use a BMS that has an active balancing function, and ensure that the batteries are connected  in parallel.
• Make sure that the batteries are at the same temperature and voltages before connecting them to the BMS.
• In most cases you'll have to wait for the battery to be fully charged up to 100% SOC, for the BMS to correctly balance or equalize the batteries that are connected in parallel. 
• Last, but not least ensure that all batteries that are connected in parallel are on the same changelog of the latest firmware. 

By following these tips, you can help to ensure that your batteries are properly balanced before or when connecting them in parallel. This will help to extend the lifespan of your batteries and improve their performance.