Raspberry Pi Forums

Hey, I'm not that familiar with the power side of things so just wanted to check if my understanding is okay here before jumping in...

I currently have a Pi4 in a 3D printed enclosure along with a powered USB3 hub (with 2 HDDs connected). Everything is running fine from a power point of view given the hard drives are running off their own power source and the Pi off a suitable source itself but I'm now looking to add a little extra cooling to the enclosure.

I currently have a fan shim attached to the pi (which is rarely triggered) but I'm hoping to add two small 30mm 5v fans to either side of the rear of the case. Is it okay to power all 3 of these fans from the Pis 5V pins? I've connected one to the 5V and GND pins above the fanshim and it appears to be okay, just wondering would it be okay to add the third fan off the remaining two 5V and GND pins?

The shim uses ?A and the small fans use 0.18A each so around 0.54 A overall between them if all running at once (which is less than an unpowered HDD would use off the usb port which generally seems to be okay).

Thanks!

If you are using an official psu to power the pi then there is about 1A available for use on the 5V pins.

So you should be ok powering your fans from the 5V pins just make sure you get good quality 5V fans some user's have suffered pi damage from cheap 5V fans failing.

pcmanbob wrote: ↑

Fri May 15, 2020 2:38 pm

make sure you get good quality 5V fans some user's have suffered pi damage from cheap 5V fans failing.

pcmanbob tends to be somewhat excitable and prone to engage in F.U.D. Not that often and IME forgivable with all the good work he does accomplish here.

I use only the cheapest chinese fans (hundreds of them, many different brands) and actually design those internal circuits for a living (can you say 'Allegro'? lol) but can't imagine a case where failure of windings or the BLDC controller IC itself would damage anything.

If you intend to fit three fans to cool your Pi, that means you intend to run your Pi to it's limit . This is unwise , as the current load
of three fans running at the same time must be added to your total load, Suggest you use the Pi just to switch out/put signals
to your project using buffer stages , incorporating a separate power supply. No fans needed , don't use your Pi as a power house

If you do fit fans to your Pi and you use control to switch fans On and Off , Low power signals don't like inductive circuits
switching ON & OFF.

Regards BoyOh

Nah I'm not running the pi anywhere near its limit at the moment. It's headless and averages about 8-10% CPU and a consistent 1GB RAM usage (out of 4). It's okay at the moment and runs on average around 54 degrees with a max spike of 62 rarely. But I'd rather keep my electronics cool if possible, especially given they are also in a case with a couple of USB drives also producing heat (the idea was to position the second fan against those but it's easy to get the power from the pi).