Power module for MacArthur HAT in Raspberry 5

[SVTwister]

For those who might want to switch back and forth between 12V-5V power module on the MacArthur hat and 5 V USB power supply (like you might if you take the Raspberry pi from your boat to home). It is important to disable the "Shutdown" and "power off" buttons in the GPIO settings and restart (to save the settings) while connected to 12 V. Otherwise the Pi will shut down almost immediately after starting using the USB power supply. 

Feel free to delete this post if this is obvious, incorrect, or covered in the instructions.

[Adrian]

Good point.

When getting stuck with only 5V and the automatic shutdown enabled, a workaround is to jumper the shutdown pin (GPIO21, pin 40) to 3.3V (pins 1 or 17). This will have the same effect as 12V SW being connected to 12V.

[aitonos]

Hi all,

I’d like to share my experience in case it helps others, and also to ask for advice.

I’ve been suffering power-related issues since I got my first Raspberry Pi 5. So far, this is my fourth Pi 5:

• 2 units were completely fried during so many times I tested them , conect, disconnect, etc
  
• 1 is working fine
  
• 1 is “under surveillance”
  

I’ve been an OpenPlotter user since 2020, starting with a Pi 4 + Moitessier HAT, which worked reliably and is no longer in use.

After months of random reboots, freezes and instability, I went through endless hours of troubleshooting, theories, and trial-and-error tests. Eventually, I decided to replace almost everything:

• New Raspberry Pi 5
  
• New MacArthur HAT
  
• New Power Module
  

I reused the same NVMe, and with this new setup the system now works perfectly:
no reboots, no hangs, rock solid.

Now I’m testing the old setup (about 11 months old):

• Old Raspberry Pi 5
  
• Old MacArthur HAT
  
• Old Power Module (not 100% sure if it’s the original one or the replacement bought with the new setup)
  

Here’s the key point:

• Powered via 5 V input → everything works fine
  
• Powered via 12 V input → system collapses, can’t even complete a full boot
  

So the Pi boots and runs perfectly on 5 V, but as soon as I use the 12 V input, it becomes completely unstable.
At the beginning, this “old” Pi 5 was also working reasonably well, except for the Maiana AIS, which for me has never been very reliable (I’m considering the desoldering mod). Later on, the whole system started giving serious trouble.

My next step is to cross-test this power module with the new setup to identify whether the issue is:

• the power module itself, or
  
• the MacArthur HAT 12 V input stage.
  

So...

1. Is there any reliable way to test the Power Module and assess its health/reliability?
   
2. Is continuous 24/7 use in a boat environment with AGM batteries harmful for the Power Module + MacArthur combo?
   
3. Could it be that the MacArthur HAT “doesn’t like” the 12 V feed, or that its 12 V input stage is damaged?
   
4. Is there any known fix or recommended workaround?
   

Any insight from people with similar marine installations would be very welcome.

Thanks a lot in advance!

[Adrian]

Unless you have heavy power consumers connected to the USB ports of the Pi, the power module should be able to run the Pi 24/7.

One common issue that I've heard about are undersized or improperly connected wires on the 12V input. 3A at 5V translates to about 1.25A at 12V. There can also be quick bursts of power consumption, especially while the Pi starts up, or does some heavy processing, which may cause sudden voltage drops with undersized and/or very long wiring.

I'd go with at least 24 AWG (~0.6mm diameter). Also use wire ferrules to ensure good and secure connection in the screw terminals.

[aitonos]

Unless you have heavy power consumers connected to the USB ports of the Pi, the power module should be able to run the Pi 24/7.

One common issue that I've heard about are undersized or improperly connected wires on the 12V input. 3A at 5V translates to about 1.25A at 12V. There can also be quick bursts of power consumption, especially while the Pi starts up, or does some heavy processing, which may cause sudden voltage drops with undersized and/or very long wiring.

I'd go with at least 24 AWG (~0.6mm diameter). Also use wire ferrules to ensure good and secure connection in the screw terminals.

Thanks, Adrian.

It is not the cables as they are thick enough. Last night I left the pi5 on overnight without hat nor any attached device and powered by USB and it also failed, so maybe it's a defect in the Pi5. However with 12V, it goes down very fast.

Is installing a Dc to DC 12 to 12 V regulator a good way to protect the PI from spikes from pumps, starting engine, etc?

I'll try the Mac Arthur Hat with my old PI4. Let's see

Thanks!

[aitonos]

HI!

I have done many tests, and these are my (no) findings.

PI5:

• without Mac Arthur hat: Works perfectly with NVME HAT or direct Micro SD. Power, logically by USB.
  
• with Mac arthur: Both with micro Sd and NVME as Hrd disk: With USB power, hangs very fast, even without anything else connected (just logitech Keyboard and Mouse  USB dongles). With 12V power sometimes goes ok, sometimes drop. This has been tried with 12V from the boat, or with an AC/DC power supply capable of 12 V - 7A
  

PI4:

•  with Mac Arthur: works very well with USB power, and with 12v from AC/DC transformer 7A. 
  

Wires are good and thick, and fails both on the boat or at home .

GPIO pins are OK in the PI5.
GPIO Height extention gets pins tightly, in PI4 works without trouble.



Why the Mac Arthur is just troublesome in this Pi5? 

Thanks

[Slovak]

The specs for the MacArthur HAT power supply indicate input voltage of 5.3 - 50V. Our boat is 24V (nominal), so there should be no problem with the HAT, despite all references being to 12V supply? 

Does the "12V SW" referenced in the documentation actually require 12V, or can it be the same as the 24V to the HAT power supply?

[Adrian]

The specs for the MacArthur HAT power supply indicate input voltage of 5.3 - 50V. Our boat is 24V (nominal), so there should be no problem with the HAT, despite all references being to 12V supply? 

Does the "12V SW" referenced in the documentation actually require 12V, or can it be the same as the 24V to the HAT power supply?

While the Pololu power module itself can handle 24V, the MacArthur HAT is only designed for 12V operation. There is over-voltage protection circuit on the MacArthur HAT between the 12V connector and the power module, which will trigger if connected to a 24V system. Best case the resettable fuse will trip, wort-case you may blow out the 14V TVS Diode D1.

---

Why the Mac Arthur is just troublesome in this Pi5? 

From what I know, there are many people operating the MacArthur HAT with a Pi 5.

If you even have problems when running from a USB supply, make sure that the USB supply is properly sized for the Pi5. Ideally, using Raspberry Pi's official USB power supply.

Another possible problem could be heat. The Pi5 produces quite a bit more than the Pi 4. Stacking a HAT will negatively impact air flow. The official active cooler may mitigate that problem.