The present disclosure provides a voltage balance and protecting method for battery modules, including a serial-charging step and a separating-charging step.  The serial-charging step is to provide a first current to a plurality of batteries of each of the battery modules and to provide a second current to the battery having the lowest voltage of each of the battery modules.  When any battery of the battery modules has a voltage equal to or greater than a predetermined voltage, a controller of the corresponding battery module sends a stopping massage to all the controllers of the battery modules to stop the first current.  In the separating-charging step, the CAN bus control module sends an activating massage, and the batteries of each of the battery modules are arranged by the voltage thereof.  The second current is provided to the batteries following the arrangement.  Therefore, the balance problem of the battery modules can be solved.

This patent manages cell imbalance problem in both charging and discharging stages based on the same globally active balance module.  A two-staged charging and balancing scheme compensates cell inconsistency in the charging stage and evenly charges each cell to full state without overcharging any cell.  Since each cell in any module is fully charged to achieve cell balance within a battery module by the current method, balance between battery modules is also met without additional balance circuits and efforts.  While discharging, a selective balance method is achieved through an external power source injecting balance current to weakest cell in the series.   Test results show the proposed balance method is capable of increasing battery range by 10%~15%.

This patent manages cell imbalance problem in both charging and discharging stages based on the same globally active balance module.  A two-staged charging and balancing scheme compensates cell inconsistency in the charging stage and evenly charges each cell to full state without overcharging any cell.  Since each cell in any module is fully charged to achieve cell balance within a battery module by the current method, balance between battery modules is also met without additional balance circuits and efforts.  While discharging, a selective balance method is achieved through an external power source injecting balance current to weakest cell in the series.   Test results show the proposed balance method is capable of increasing battery range by 10%~15%.