Link: FAQ: How to prevent sparking? (Antispark current)

When you connect the motor controller to batteries severe sparking often occurs. This is caused by the internal capacitors inside the motor controller circuits. The PDF file explains a simple method how to prevent sparking.

The RT-BMS allows to switch on the anti-spark connection before the main current switch is connected. (RT-BMS Master unit - connector B4 - Antispark Current)