I have 2 separate projects one is a case for a Raspberry Pi 3b+ as NAS server and the other is a media cabinet.

The NAS kit has 4 30mm 2-wire fans (5V 180mA) and a wired in USB cable that is plugged into a 5V 2A USB wall adapter and a 2 pin switch rated up to 16A. 3 power cables, 1 for fans, one for RPi, one for Power Hub for drives. I get the fans to spin but slower than the specifications. The other project is 5 120mm (12V 250mA) with a 12V 2A wall adapter, again more than enough.

I have not tested the second project but want to have an answer just in case. There is plenty of current and the voltages are correct for the components.

I am just not sure as to why there is such a notable drop in speed or if there is a way to increase the current without another lead to run a transistor.

Here are the links to the components:

Edit: To clarify, only the fans are plugged in to usb wall adapter for project one, the RPi and the hub have their own power supplies.

  • \$\begingroup\$ If the fans are wired directly across the 5 V rails, then the power supply is not providing sufficient current for the Raspberry Pi and the fans. Get a bigger wall wart, or lesser Pi, which eats too much current. \$\endgroup\$ Mar 12, 2020 at 4:01
  • \$\begingroup\$ Thank you for the response. It is only the fans connected to the wall adapter. Each device has its own power supply, i did this to also prevent damage to the RPi in case the fans caused a sudden change in voltage or current \$\endgroup\$ Mar 12, 2020 at 21:16

1 Answer 1


Found the answer, one of my fans were in series by mistake and caused a drop in voltage.


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