Making Things – Richard Nuckolls Professional Site

September 5, 2023February 14, 2024

How to Build Your Own Portable Power Station

battery box sitting on a stone in a field — DIY portable power station

I love my portable power stations. I recently saw a 12V LiFePo4 battery on Amazon Vine, along with several other 12V accessories. That triggered an idea for making a brand new battery box myself. I wonder if I can make the power station out of parts I get entirely from Amazon Vine?

I’ll walk through the steps I took in making my own portable power station. Now I’ve got another option for reliable power wherever I go. You can make you own too.

What is a Portable Power Station?

A portable power station is a device that can provide electricity on the go. It is essentially a battery pack that can be charged using solar panels, wall outlets, or car chargers, and then used to power electronic devices like smartphones, laptops, cameras, and even small appliances like mini-fridges or electric grills.

The main advantage of a portable power station over traditional generators is its fuel source. It does not require any fuel or oil to operate and does not produce any harmful emissions. This makes it an ideal choice for outdoor activities like camping and hiking where you want quiet, clean power .

The most important decision when choosing a portable power station is how much power (wattage) is available. A laptop and a coffee pot take only a little power. A blanket or a kettle takes more. If you want to run a refrigerator or a space heater all day you need a much bigger system. Luckily UL listed electrical appliances list their wattage use.

Uses of a Power Station

Camping

I use my Jackery 500 every camping trip. It powers LED lights, charges my phone, my camera batteries, headlamp, and rechargeable flashlights.

On my first trip this summer, I used it to run a mini-fridge, which I got on Vine. The mini-fridge takes a lot of power; I ended up using the Jackery one day, my Bluetti EB3A the second day, and recharging both from the truck alternator. But it kept the meat and sodas cold!

battery box powering electric kettle — Boiling water with Joulle kettle and Jackery

Cooking at the campsite has never been easier. I have a 5 cup Mr Coffee coffee pot for coffee. It also makes good soup and heats hot dogs. I have a Joulle 500W kettle to boil water, make oatmeal, and pop corn. My favorite appliance is the Dash mini griddle. I’ve tried

mini quesadillas
ground sausage
hamburgers
pancakes
scrambled eggs

Having 120V electric appliances at camp means you don’t need a fire to cook.

My favorite use while camping has to be running a 12V electric blanket. I have a blanket with a 1 hour timer. I turn on the blanket, get warm and fall asleep, and the blanket shuts off automatically.

Around the house

I also take my power station all around the house and garage when I’m tinkering.

Nissan Xterra with the hood up, tools in the foreground — Jackery running a soldering iron

Plug in a lamp for more light
Vacuum the truck
Heat soldering iron for wiring
Run a pump sprayer to wash the truck
Trickle charge a battery

Power without an extension cord is very convenient.

Power outage

When the house power fails, having portable power stations really shines. Just like when camping, I can cook and have light and a warm blanket. More importantly, I can run my laptop all day if needed. For a remote IT worker, this is critical.

Components

Battery

I saw the FLLEEYPOWER 12V 6Ah LiFePO4 Battery on Vine. Its small capacity meant it wasn’t going to run big loads for hours. P=IV, so 144W would use 12 amps (12A) at 12 volts (12V). This battery is only rated for continuous discharge of 6A in 1 hour, or 72W, and 144W for 3-5 seconds. The dimensions are small though. I thought it would fit in an ammo can.

12V Output DC Power

You’ve seen them. The round 12V socket, a.k.a the cigarette lighter outlet. A common 12V fitting on all cars. My truck has 4, one of them I installed myself on the rear bumper.

You can plug in many car accessories. USB chargers, portable vacuums, tire inflaters to name a few. Most any automotive parts shop will carry a panel with a pair of USB ports, a 12V socket, and a couple of switches. I got the FXC Blue 3 switch panel from Vine.

120V Output AC Power

The big deal in portable power is AC power, or line power, or 110 power. It’s the power you get in your house when plugging a TV into a wall socket. It’s provided by the local electric utility company via the electric grid. In portable off-grid systems AC power comes from inverters.

Inverters transform 12V DC current into 120V AC current. Refer the Edison vs. Tesla cage match. For AC power on the battery box, I only had a few amp-hours of capacity, so I settled on a low power inverter. The Bapdas 200W car inverter fit the bill. Plus it has a voltage display.

Fuse Block

Current flows cause heat. Heat causes fires. Circuit protection stop fires. Fuses protect 12V circuits.

A fuse block combines separate circuits, easy fuse replacement, and common neutral bus bars. Separate circuits lets you add multiple switches and different sizes of fuse depending on load. I got a 6 fuse block from POWO Carlife.

Switch

Who doesn’t like a chunky switch? When I saw the tall 100A shutoff switch from Autoxbert I knew I was going to drill a hole and mount that switch inside the box. Most of the fancy electronic power station have a push button on/off switch.

Case

I thought an ammo box, a tackle box, or some other type of lidded box a handle would work well. Plastic would be cheaper and easier to modify. I couldn’t find what I was looking for on Vine, so I ordered the Sheffield ammo can from Amazon.

I made sure I had the measurements for the battery, fuse block, and inverter before ordering the box. Everything needed to fit inside or outside, on the sides or top. Round divots in the lid, the same side as the chunky switch, solidified the selection.

Solar panel

The ultimate off-grid power source is a solar panel. But solar panels are tricky in this case. For a 12V system, most “portable” panels are the size of 2 pizza boxes. Most of the panels showing up in Vine are 5V 3W-5W. Way too small to power even this modest system.

Charge controller

Bigger solar panels usually run at higher wattages with more variability. For example, a typical residential panel generates current from 12V on cloudy days to 18V in full sun. A charge controller regulates this voltage fluctuation and provides the correct voltage to the panel. I did find a 10A controller from Enovolt on Vine.

Light

Ever wanted a flashlight that will run for days? Every power station comes with a light. I had a 12V LED light in my electronics grab bag.

Construction

Measure once, cut twice. I think that’s how it goes.

The construction process began once all the materials had come in. First I stuck the battery, fuse block, and 12V sockets in the ammo can to make sure it all fit. I try to take into account routing and bending wires.

I broke the three switches that came with the 12V sockets at this point. The set was fully wired from the factory. But not how I wanted it wired. The wire lugs were firm. So I ordered some small but fine metal switches.

Next comes drilling holes. You don’t want to run a drill bit into the battery once it’s mounted. The cutoff switch was an 1/8″ larger than the divot. Nothing that a step drill bit and steady hand won’t handle. The light switch went in on top too.

The base plate for the 12V sockets was just wide enough to require cutting the lid bracing. Because I had already tossed the switches, I tossed the plate and mounted the sockets directly to the ammo can. I already knew how far into the can the sockets and wire projected.

I prefer to solder and shrink wrap connections. This gives a stronger joint. But ring terminals make it easy to wire a fuse block. So I solder the wire to the ring.

wires with crimped ring terminals showing soldered connections — For crimped terminals, solder the wires for extra strength

The inverter is mounted on the outside of the can. I settled on one side instead of the top. So I removed the 12V plug and drilled a hole for its cable. I put a hole opposite this for the solar panel cable. I planned to mount the charge controller inside.

The last hole was for the LED light. I found a vertical orientation worked best because the leads were centered and lay behind the lens. And the battery was directly behind the light, I moved the light to one edge so the hole would clear the battery.

After all the holes were drilled, it was time to lay out the wiring. Wires run from the battery to switch and fuse block. Wires lead to the sockets and light and switches and inverter. Wire to crimp, wires to solder, terminals to screw down.

wires and fuses in the fuse block — The fuse block sits between the battery and 12V sockets

Final mounting used some bolts, some flanges and nuts, and some feet of double sides tape. Overall it feels sturdy, but I wouldn’t want to drop it.

inverter with double sided tape on back — Double sided tape on inverter

Testing

I did a test of the wiring one leg at a time. Everything worked!

The LED light is not very bright but draws very little power.

The inverter displays the battery voltage, and loads over 100W run on it for a short time.

Both 1A and 2.5A USB chargers work. I ran the mini-fridge on the 12V outlet for about 15 mins and was satisfied.

The cut off switch is sturdy with a chunky feel. It works exactly as advertised. I’d like to add a custom cover to the terminals.

Neither a 5W nor an 8W solar panel I bought from Amazon were enough to run the charge controller. I’m considering buying a much bigger panel that’s capable of making 15V+ in direct sunlight. For now I’ve got a LiFePo charger to directly charge the battery.

Cost Breakdown

120V Inverter $25
Case $10
Switch $7
Small switches $12
Battery $25
Solar panel $18
Charge controller $40
Fuse block $11
12V sockets and switches $24
Total $172

This project ended up costing the same as a similar power station with a bigger battery and without the solar charging. If I did it again, I’d leave off the solar and get a LiFePo charger and larger battery.

A portable power station is a convenient and reliable source of power for anyone. I made one using inexpensive parts, the most expensive being the optional solar charge controller. Whether camping, working around the house or during a power cut, a portable power station shouldn’t be out of reach.

Thanks for reading. I had a lot of fun building this battery box: 4 full evenings after work to get it ready for a Friday camping trip. If you want to build one of your own, I’ve included Amazon affiliate links to the specific products I used. If you buy one, I get a commission but it doesn’t cost you any extra.

September 29, 2020

Building the X Desk

wooden desk with dark wood grain — Finished X desk

When my wife and I changed spaces in the house, I gave her my desk. That left me without a place for my computer. I decided I could make one.

I’ve got a compound miter saw, a drill with a Kreg jig, and a tape measure. Lowes provided the lumber.

The X Desk design comes from Ana White’s website. I modified it to make the top shorter. I wanted a lighter desk that was easy to move. Except for the top, the entire desk is made from 2×4 lumber. I chose some 1×12 pine boards for the top.

The biggest feature of the desk is the dramatic cross braces used on the single leg of the desk. Because I have a miter saw, I knew I could cut these pieces easily. I even made a modification to the design to support a narrower support. The back braces now angle 22.5 degrees.

Craftsman miter saw — I cut both 22.5 and 45 degree ends

I made a decision on the top; instead of screwing in from the bottom, or countersinking screws in the top, I would use bolts. I thought flat bronze crowns for the bolts would make nice accents. Bolts would make taking the desk apart possible too.

Clamping wood — A clamp holds the wood in place before drilling a hole

The challenge with bolts was the top layer of the legs. Two 2×4 and two more 1 inch boards meant about 4 1/2 inches to drill through and run a bolt through. I chose a trick. I embedded a T nut in the bottom side of the top leg 2×4. The nut is buried in the leg and won’t get lost. The bronze bolts run through holes in the top and holes in the leg and into the nut. Perfect.

I gave the desk a light sanding before applying stain and wax. I should have bought an electric sander and given the whole thing a finer finish. About two weeks later the wax finish has just about dried. I could clear it off and give it a good polishing. I’ve been enjoying it for more than a week now.

pieces of wood and a drill — The first set of cut pieces are ready to join

September 10, 2020September 29, 2020

Want Better Results? Use the Right Tools

Scientists are measuring the effectiveness of face mask materials. Most are using lab-quality expensive equipment designed to get absolute measurements and prove a very narrow hypothesis. But not all studies follow this pattern. A group of scientists and engineers from Duke University have released the results of their experiment using a low-cost method of analysis. They did it on the cheap.

The experiment uses common tools. The researchers used a laser, and cell phone, some custom software, and a guy wearing a face mask. The study follows standard practice for analysis and presentation, but the materials list seems one step above buying some materials at a hardware store. I found this intriguing. I’m going to recreate the experiment with stuff from the Dollar Tree.

My Build

I collected supplies from Dollar Tree. Three black foam boards, a plastic Fresnel lens, and a LED flashlight were the main items. I also got a laser pointer and a hand-held fan. To these I added a mobile phone from my current set.

I built the box based on several measurements. The first is the field of view of the camera used. I wanted the camera to capture as much of the spread of droplets as possible while minimizing extraneous elements like the walls. Spit floats a lot.

The Fresnel lens was measured next. The box needed to be wide enough to hold the entire lens, and deep enough to allow focusing of the light to occur in the center of the box. This would illuminate droplets in the narrowest horizontal and vertical slice. I wanted the spread of light from the flashlight to be the most concentrated halfway between the speaker and the camera. The Fresnel was 6.5” wide by 9.5” long and focused about 9” away. It’s strong enough to light a fire with sunlight.

The last dimension was the minimum focal distance of the camera. The box needed to be large enough that the center was within the focusing range of the camera. The minimum focal distance for the first phone I tried was 2.5”. Because the distance was so short, I felt fine making the box larger than 5” square. I didn’t need to make the box huge either.

I made full use of the 20”x30” boards. The box measures 14.5” on each side. This made it easy to center the light channel, but just kept the side walls within the field of view of the camera.

black box with open panel — Labeled box for experiment

I mounted a mobile phone to the rear panel of the box. I cut a small hole and aligned the camera lens. Low tech painter’s tape sufficed to secure the phone while still allowing access to the buttons and screen. I could even see what’s in the box.

mobile phone taped down — Mobile phone affixed to box

I used water in a spray bottle to test the setup. This produced a consistent heavy spray of large and small droplets. With light passing through the lens in a beam, the droplets become visible within a horizontal bar across the middle of the box.

I tried two mobile phones to record video. Each frame can be analyzed. Video should allow identifying the start of droplet production too. Because the box has depth the droplets must travel some distance to the light beam. Using the audio track I could count the travel time in frames. The first phone, a Nokia Lumia 920, was not sensitive enough to capture droplets. The second phone, a Google Pixel 2, captured the test spray but no unmasked control droplets were visible. It’s time to try something else.

I tried a second light source. The original experiment used a laser with a beam spreader to project a horizontal plane of light across the box. I didn’t have access to a beam spreader, but I recalled another device that uses a plane of laser light: LIDAR. A LIDAR sensor uses a spinning mirror to reflect a laser beam in a circle. I could use the same principle of high-speed rotation to make a relatively continuous plane of laser light. Enter the laser fan.

I picked a red laser pointer out as a light source. These lasers are low power and relatively safe even with direct exposure. I also picked a battery operated hand-held fan to rotate the light source. It seemed easy enough to just mount the laser on the rotating axle of the fan. With that, a bit of tape depressed the ON button to engage the laser.

a laser pointer mounted on a small fan — Spinning laser of geometry

With the laser engaged, I needed to take care that I didn’t get a harmful exposure to my eyes. I crafted a set of laser safety glasses from a pair of clear safety glasses and six layers of blue cellophane. This attenuated the bright red laser to a faint dot when shown through the glasses. With these glasses covering my eyes, I started the laser spinning, the video recording, and produced a test spray. The following GIF shows what was captured from one of the tests.

droplets illuminated by laser — Frame capture of laser droplet illumination

But I could get enough exhalation droplets to count. Even with a promising result with the test spray, no speaker droplets were recorded on the video. So I increased the quality of the equipment. I moved to using a 60W LED bulb in a lamp for the lighting, and a DSLR for the camera. I cut a big hole for the new camera and started testing again.

Even with the DSLR, video capture did not produce usable images. Test sprays emitted sufficient droplets, but regular speech did not. I eventually set the camera to burst mode for JPGs, at f/2.8 and 1/60th of a second. I also started blowing raspberries.

These changes made it possible to reliably capture droplets for comparison. I counted droplets from three sets of four images: a control without mask, a neck gaiter, and a two layer cotton mask. I used a blunt discernment for categorizing the droplet size. Droplets were either small and looked like dots or large and looked like strings. Droplets out of focus were ignored.

exhaled droplets captured in beam of light — Exhaled droplets captured in beam of light

I’ve tabulated the results in a table. This makes the tabular data more rectangular. I also threw in some statistics because math makes everything more credible. Actually, the margin of error calculations reveal a lot of variability in the cotton mask test.

	Image 1	Image 2	Image 3	Image 4	Averages @ 95%
Control	31L, 3S	20L, 8S	32L, 9S	28L, 4S	28L±4, 6S±3
Gaiter	17L, 7S	27L, 3S	31L, 6S	33L, 0S	27L±6, 4S±3
Cotton mask	34L, 33S	18L, 30S	4L, 25S	10L, 10S	17L±11, 25S±9

Large and small droplet counts for three masks

The results of this test are surprising. The gaiter seems to make little difference in overall spray. The cotton mask does seem effective at reducing large droplet spray, but at the cost of greatly increased small droplet spray. Small droplets are expected to float in the air longer, and therefore pose an increased risk of airborne contamination over large droplets. This differs from a finding of the original study, which showed small droplet count higher for the gaiter than any of the other masks. The cotton mask also has a much higher margin of error than the other samples. Maybe spitting in a mask doesn’t work reliably.

This was an interesting build for me. I wanted to see if I could validate a scientific paper. I wanted to see what I could learn about the masks I had. I wanted to go to the Dollar Tree, because everything’s one dollar. The process reinforced my belief in the scientific method, and the cause of science in general.

Many things can go wrong.
You need to be diligent in your testing process.
Sample sizes matter.
Keep an open mind, because your preconceived notions may be wrong.

I also found that I could not replicate the experiment using only low-cost materials. Science experiments often require precision equipment that hobbyists don’t need. Determining an analogue for a squishy human action increases consistency. This was very evident in exhalation droplet production. But I was very pleased to capture images both with a laser beam and a focused light source. Yeah science!

August 27, 2020September 29, 2020

What I Learned From Documenting How to Make Coffee

brown liquid pouring on black and white ceramic mug selective color photography

I was sitting on the patio of Yoolks On Us, having just ordered breakfast. I tasted my cup of coffee and exclaimed “Hey, this is good!” I don’t have high expectations of coffee at most places, but I hold out hope.

I’ve tried coffee at gas stations. I’ve tried coffee at big coffee shops. I rarely had coffee I liked until I started making my own.

My story starts small. A friend gave me a bag of coffee to consume. They were leaving on a trip and would not be back before it lost its luster. I found an unused name-brand drip brewer in a cabinet at work. After a thorough cleaning, I made my first cup. It was okay.

I thought the problem with coffee was that I didn’t like it. Surely places that sell coffee by the cup take the time to make it properly? This is a testable hypothesis. So I decided to sample a variety of beans, made in a consistent manner, according to best practices for the drip brewer, and document my experience. This began four years ago.

Assuming the coffee brewer was working correctly, I formulated my method.

Brewing: I read the manufacturer’s directions for using the brewer.
Precise measurements: I made a measuring cup marked for 4, 6 and 8 tablespoons so I could quickly measure the coffee grounds. I also got a graduated cylinder, a baby bottle, to measure water in 2 oz increments.
Quality water: I sourced water from the office water cooler. It tasted much better than the tap.
Testing ratios: I first tested the coffee to water ratio specified on each bag. Then I tested double and half ratios. The standard is 1 tablespoon to 4 oz. of water.
Timing: I set a timer of 18 minutes to get the first cup of coffee. This allowed the brew to finish while not sitting in the carafe too long.

“The difference between screwing around and science is writing it down.”
Adam Savage

Each time I bought a new bag of coffee, I would add it to my chart. The chart included the name of the coffee, each ratio, and my judgement on taste on a scale of -2 to +2. I tried approximately 20 brands of coffee over the next year. Here’s what I concluded.

Most coffee is hot and bitter

I can’t drink hot coffee. Why would I want to burn my mouth? I always let the coffee cool. When it’s too hot I can’t taste it. Sometimes this means waiting 30 minutes or more after buying a cup.

Most coffee I’ve tried is too strong for my taste. On top of that, it’s usually too bitter. The rare exception is coffee sold as a “Breakfast Blend.” This blend is usually light or medium roasted. I assume these three observations are connected.

I found an objective explanation while trying Maxwell House Boost coffee. I had tried light, medium, and dark roasts before. Dark roasts present the most bitter cups, but sometimes the coffee is still good. Maxwell House Boost is a medium roast which claims to have 25% more caffeine. The coffee tasted fine at all ratios, but with more bitterness than expected. I think most coffee sold by the cup is chasing more caffeine and flavor by making it strong and dark. More caffeine and darker roasts make the coffee bitter.

Coffee is different around the world

I found three distinct types of coffee beans during my testing: Columbian, Ethiopian, and Sumatran. There’s also the generic Arabica, which is just coffee grown anywhere. Most coffee I’ve tried in America that’s trying to elevate itself is labelled “100% Columbian.” The differences seem to come down to flavors that come out from the soil and the harvesting in these places.

I found Colombian coffee to have a robust and traditional coffee flavor. Ethiopian coffee has a fruity character. Sumatran coffee has some different flavors that I find off-putting. Most of my testing was done with generic Arabica coffee, and most of it was generic tasting.

Consistency matters

Because I made the same coffee over multiple days for comparison, I wanted to make consistent measurements. I learned that “heaping tablespoons” could vary greatly from one scoop to the next, so I settled on 2 tablespoon increments.

I realize now that I could have gotten a scale and done everything by weight instead of volume. This would have provided the highest level of consistency. But my test equipment worked well enough.

I found that the best ratio for brewing varied with the brand of coffee. In most cases, I found 1 tablespoon to 8 oz. of water yielded the best tasting coffee. Usually the 1 to 4 ratio would also be fine, if the coffee itself was good. Using 1 tablespoon for every 2 oz. of water would make a good tasting cup worse, and would not make a weak coffee bean taste good. If the coffee is bad nothing will save it.

I found I can drink properly prepared coffee. When the beans are good, and the roast is mild, and the strength is moderate, I enjoy the experience. I just needed to figure out what good coffee meant to me.