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

enter image description here

  • \$\begingroup\$ Where is the output node? Where you measure the output? \$\endgroup\$
    – CNA
    Commented Apr 5, 2018 at 4:40
  • 2
    \$\begingroup\$ In your diagram there is no connection between arduino ground and Li-ion ground. You will need that ground-to-ground connection for this to work. \$\endgroup\$
    – user57037
    Commented Apr 5, 2018 at 4:49
  • \$\begingroup\$ My apologies for omitting that in the diagram, it is connected GND to GND \$\endgroup\$
    – sryan2580
    Commented Apr 5, 2018 at 5:46
  • 2
    \$\begingroup\$ And how is it possible to get 8.7V if grounds are connected? \$\endgroup\$
    – Jogitech
    Commented Apr 5, 2018 at 6:23
  • 1
    \$\begingroup\$ Maybe your fet and battery is connected reversely to the rest of the circuit and someting is wrong with the connection of the grounds? Cant see another way how you can get 8.7V at any Point of the circuit \$\endgroup\$
    – Jogitech
    Commented Apr 5, 2018 at 8:31

1 Answer 1


I found my problem! It turns out that the GND trace on the Arduino was damaged so the Battery GND was indeed not connected to Arduino GND. Seems to work now Thanks for the help!


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