Can somebody explain to me why this circuit will not work? It might be that IRF3205 isn't a great choice for an Arduino but it works for Adam Welch on youtube so it should be possible. Tried it even with a 10k resistor gate to source.
When I measure it when the gate goes LOW:
Gate is 0v
Drain is 3.7v
Source is 3.7v
When I measure it when the gate goes HIGH:
Gate is 5v
Drain is 8.7v
Source is 5v
EDIT: Missing in the diagram is the ground to ground connections