MiniBMS Head End Board is required to process signals from cell modules and control the charger and motor controller as well as buzzer alerts. Only one Head End Board is required for each EV. See Product Support page for detailed documentation.
In some cases you may prefer to have an onboard buzzer, if your head end board located such that the driver can hear the buzzer, for example on a bike or scooter. If the head end board located under the hood of a car, then you would likely want a remote buzzer mounted in the cabin. Select the buzzer option which best suits your needs.