Computers do stuff really fast.

But they also create heat. That’s especially an issue with laptops - as the temperature goes up, the fan ramps up, and here be dragons. It gets loud. Also your computer may throttle its performance to maintain a temperature ceiling.

I’ve been using an 80mm USB fan that’s sort of just taped onto the back of my laptop, blowing cool air through the grille of the case onto the heat pipes. I wanted to build an array of fans that could attach to the back of my laptop (magnetic strip?). Since the grille of my Dell Latitude 7390 is around 200x40mm, five 40mm fans positioned side by side would be good.

I also wanted to be able to power all of the fans off the laptop - so either through USB or USB-C. The standard USB connector should be adequate, and provides 5V @ 500 mA. There exists 5V 0.1A DC fans, so I went ahead and purchased a few of them off AliExpress.

When these arrived, the first thing to do was to take the wires out of their molex connectors.

A little paper clip pushed into the spring clips did the trick.

Next, was to dry-test the fans to make sure that they all worked.

Five fans connected in parallel
Left multimeter measuring voltage across the fan +ve and -ve
Right multimeter measuring current through -ve

This is where I ran into a rather bad problem. I was reading 4.89V @ 0.11A through all of the fans.
All of the fans.

Each of the fans were meant to draw 0.1A, however it turned out that each fan was only drawing 0.03A!
They barely had enough energy for the fan to start spinning; with a little help (manually spinning the fan), they did spin - but oh ever so slowly.
I could hardly feel a breeze, their CFM was close to zero.

Unfortunately this predicament was a project stopper - the fans are unusable.
Perhaps it was just this YAKOO brand of fans. I might try to purchase a few SUNON branded 40mm 5V fans, as that brand is reputable.