The GYD-9E module contains internal inductors and capacitors. Do not apply reverse polarity or voltages above 30V, even momentarily. 4. Electrical Characteristics (Typical at 25°C, Vin=12V, Vout=5V) These values are representative of a healthy GYD-9E module:
A: No internal protection. Add an external Schottky diode in series with input if needed. gyd-9e datasheet
A: Not recommended. Slight voltage differences cause current hogging. Use a single 5A-rated module instead. The GYD-9E module contains internal inductors and capacitors