There is a simple fix I am using - on the end of the + lead from the ESC, I have soldered a 10 ohm resistor. I first connect the - (black) wires, then I touch the free end of the resistor to the pack + lead and wait for cca 1 sec (the ESC beeps). After this I connect the + leads, completely spark-less. The big sparks are slowly corroding the connectors, which made me do it.