Portable Off Grid Power for the Raspberry Pi

Hello Operators

I’ve had a couple of requests to describe how I power the Raspberry Pi from my portable station power, in the field.

Well there’s two parts to how I do this. The first describes how I’m doing it now, and the other describes how this will be done when the project is complete.

Todays configuration

I built one of the 4 port powerpole distribution kits from www.k9jeb.com . All four ports have powerpoles with fused DC coming from my LiFePO4 pack.

On one of those ports, I made an adapter for the Raspberry Pi. I used an voltage regulator with ~9-18v input, 5v 2A usb output. It has 15A powerpole on one end, usb out on the other. The powerlines end connects to the DC distribution board, while the other end (USB out) connects to the micro USB port of the Raspberry Pi.

That’s how it’s wired now. It is also the easiest way to achieve this. Unfortunately it’s not the best. There’s a small amount of noise to deal with each time you add one of these Regulators, converters or bucks into the equation. This is always going to be an issue because our radios run off of 12 volts and the small electronics like the Raspberry Pi, run off of 5 volts. So we always need a way to drop the voltage down to something our Raspberry Pi can manage. You need to keep that in mind when choosing your components, or building your regulator. Another issue with powering the Raspberry Pi from its micro USB port is pulling the damn cable out by accident. That’s the easiest way to corrupt your SD card. If your heart is set on feeding the USB port, I would suggest getting an angled cable, and taping that cable to the case. These are those little things that people never tell you when they write their tutorials.

Future configuration

Before I explain how I’m going to do it in the future, it’s important to understand I’m also using a PiJuice hat which has a built-in battery, real time clock, and voltage regulation. It also has the ability to use an external battery pack. This is the hat so often seen on top of my Raspberry Pi. Now before you run off to my Amazon shop and start buying these things, you can achieve the same functionality with individual parts. I decided to use the PiJuice hat because it would make a much smaller package being integrated with all of these functionalities already, than if I built them up individually on my own. You’ll need to decide if all of the functionalities of my Raspberry Pi are important to you, if so how you’re going to implement them.

The PiJuice has a regulated DC input port, with a max voltage of 10v. My plan is to feed that input with either a linear or switching power supply. The linear power supply is nice because it’s quiet, while switching power supply is awesome because it uses less current. I haven’t made up my mind on which of those is more important. Naturally I’m leaning towards less noise, but I’ll come back to this topic.

I’ll replace the USB buck with a wide input voltage linear or switching converter rated at something between 5-,10v 2A output. That will be wired directly to the regulated voltage input port, on the PiJuice hat.

The PiJuice also has connections for a soft power switch. I’ll wire the cables to that port, then run then to a momentary switch mounted on the enclosure. This will give me start up, shut down, and sleep.

The internal battery of the PiJuice provides uninterruptible power for the Raspberry Pi and its peripherals. Because of the GPS, audio interface, and CAT control, the built-in battery is not going to last that long, but ensures the Raspberry Pi shuts down safely in the event of external power loss, while also providing power for the onboard real time clock. If I wanted to use the PiJuice to power of the Raspberry Pi for longer periods of time, I would use the external battery port with a larger external battery pack.

If you’re interested in using your Raspberry Pi off grid or in the field please bookmark my playlist ham radio with a Raspberry Pi.

73
Julian oh8stn
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