## Introduction: Emergency USB Power Source (3D Printed)

This project makes use of a 12V battery, like you would use for a vehicle, for charging USB devices in case of a power outage or camping trip. It's as simple as affixing a USB car charger to the battery. After Hurricane Sandy, I was without power and used an inverter/battery setup at home, but it was huge and heavy. This project revisits the concept with a smaller battery (meant for motorcycles/ATVs) and DC-only charging.

I've also created an optional 3D printed battery topper to cover the battery contacts and hold the USB ports. The design is available on Tinkercad so that you may modify it to fit your specific battery and USB charger.

The compact design makes it easier to transport and store. There are many situations where this device could be useful:

• power outage
• camping
• off-grid living

## Supplies

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## Step 1: Wire It Up

First I connected the USB charger to the battery to be sure it works, and take some measurements. The red wire connects to the positive terminal, and the black wire connects to the negative terminal. My charger also has a fuse. The USB charger can be used like this without the need for any 3D printed parts. It can be installed in a motorcycle dashboard or tucked away with your other emergency supplies.

The 8Ah battery at 12V gives me 96 Watt hours. Divided by my phones 11.2 Watt hours and factoring in a 90% efficiency of the USB charger, I can get about seven and a half full phone charges from this battery, or half that if I want to still use it to start a vehicle.

Formula:

(8Ah * 12V) battery / (11.2Wh phone / .9 charger efficiency) = 7.7 charges to depletion

## Step 2: Measure and Model

Use a ruler and/or calipers to measure your battery and USB charger and adjust the Tinkercad model to fit its dimensions with some tolerance (about half a millimeter of extra space should do), if needed. Definitely double check the measurements of your components before printing—I used an old battery that I can't find online and so yours is bound to be a little different.

My battery dimensions: 151.33mm wide x 84.40mm deep x 106.00mm tall

My USB charger dimensions:

• 27.23mm diameter of threaded stem
• 37.36mm nut outer diameter

Disclosure: at the time of this writing, I'm an employee of Autodesk, which makes Tinkercad.

## Step 3: 3D Printing

After downloading the STL file from tinkercad, I used Cura software to prepare the model for printing. I flipped it upside down so it will print its flat surface first. Here are my print settings:

## Step 4: Use It!

Unplug the USB charger and install it into the hole on the 3D printed topper using its included nut. Wire up the circuit (red to + and black to -) and set the topper on battery. Tidy up the wires by tucking them up into the empty space remaining in the front of the topper.

Turn on the USB ports with the included switch before using, and turn off when not in use.

Thanks for following along! If you make your own version, I'd love to see it in the I Made It section below!

If you like this project, you may be interested in some of my others: