DC electronics safety notes
* Why are we talking about this?
* Personal safety
* Fire safety
* Preventing catastrophic equipment failure
* Wire gauge - sizing wire correctly
* Measured in AWG, bigger numbers are smaller wire
* Many wire manufacturers will provide an "ampacity" chart to talk about current rating in various wire products.
* Wire construction
* Stranded wire is easier to work with generally but isn’t as good of a conductor as solid wire. Stranded wire is also best for applications where the cable is expected to bend and move.
* Solid wire is harder to work with but has higher durability and is a better conductor than stranded wire. It’s best for applications where the cable won’t be moving a lot such as fixed installations and is generally cheaper.
* Copper wire is more expensive and is a better conductor of electricity and tends to be more durable.
* Aluminum wire is half as heavy but requires heavier gauges to carry the same amount of current as copper wire.
* Sizing wire to not be the thing that gets hot when a short circuit occurs.
* Overgauging for expected load relative to fuses or breakers to ensure the wire isn't the thing that heats up and burns.
* Fuses and breakers
* Why fuses?
* Burn out and stop the flow of current with a fusible link.
* Affordable
* Keep spares
* Why breakers?
* When the heat of an internal element is too high the circuit is broken by an element. Circuit breakers can be reset.
* More expensive than fuses.
* Automatically resetting circuit breakers exist, but many are manual and can be used as a switch to turn sources of electricity off.
* Note: When building DC systems make sure circuit breakers are explicitly rated for DC systems. AC breakers aren't an acceptable substitute here.
* Install these items as close to the thing being switched as possible.
* Covering contact points
* Why cover contact points?
* Prevents accidental shorts by having less exposed surface area.
* Cover contact points
* Wire nuts
* Electrical tape
* Heat shrink
* Quality splices (mention marine grade)
* Connectors
* Powerpole
* SAE connectors
* Keeping things dry/sealed
* Because metallic dust and water can potentially short internal parts
* Using and understanding the limitations of various sealed enclosures
* Using properly built installed sealed connectors
* Use cable glands
* Silicon / sikaflex
* Power source disconnects
* Batteries
* Solar panels
* Avoid deep discharge of batteries
* Some sort of monitoring of battery capacity used
* Varies by battery chemistry
Author: K7JLX
Solving a dorky problem – writing things down
Greetings, it’s been a while since I’ve written a post. I’ve had some things cooking in the background and have a few posts to write about some things I’ve been doing that aren’t especially interesting but could be helpful none the less. This post is about something that seems a bit silly, but is actually pretty important… the ability to easily and comfortably write things down while operating in places without writing surfaces.
I ended up stumbling across something that pilots had been using for quite some time: aviation kneeboards. The advantage of these is that they’re designed to be strapped to a leg and for situations where space is constrained like a cockpit. This concept maps nicely to vehicles or any spot where you can lay down in a supine position and bend a leg or sit. Most situations I’m in when operating in the wilderness it’s nice to not have to deal with a folding table when I’m in an odd spot or simply don’t want to carry one on a hike. As long as I can sit in a relatively normal position or lay in the back of a vehicle or on a bed it’s easy to use.
It was useful to have something big enough to easily record dozens of callsigns for one weekly net I participate in. It’s easiest to track all the participating stations’ callsigns on a single sheet of paper for easy counting and reference. A 6×9″ tablet had been working for me previously so I sought out something that could accommodate one. A company called Battle Board made a “medium” aviation kneeboard that could hold the tablet I was using. I picked this one for a number of reasons including a clipboard attachment that can be used for other kinds of documents, markers for the polycarbonate window that can be erased, and a plastic sleeve that can be used to protect maps or other documents from water. I suspect any similar device could work just as well, but this one could be used for other things I’m interested in doing.
This works by setting it on top of your leg and pulling the elastic band behind it and attaching the adjustable metal hook to some elastic bands on the back of the cloth flap with the mesh pocket. I’ve used this in a number of locations from bed with a bent leg, in a vehicle, in a camping chair, and sitting on large rocks. It works pretty well and easily slides into a backpack. It’s pretty comfortable and does a reasonably good job of staying put. There are elastic retention straps that easily secure the top and bottom of the tablet using the cardboard backing. The mesh pocket on this specific one can be used as a phone holder. It also holds a ‘rite in the rain’ notebook so it’s still useful in inclement weather.
Estimating power consumption for your equipment
Hello everyone! Today I wanted to post about a topic that is pretty important if you have an interest in off grid, grid down, or emergency communications: estimating power consumption for your equipment. This post is in part inspired by a topic I chose for the Portland Neighborhood Emergency Team chat net. Shortly after I chose this topic I got an e-mail from Kevin, N6KVN asking for some advice for setting up a portable field station, and so I figured I’d write a more detailed post about my methodology and way of thinking about operating a ham radio station when grid power isn’t available from a preparation or pre-planning standpoint.
My basic test setup consists of three components. I have a power source of some kind. This could be a battery or a wall-connected power supply. The next component is a power meter connected between the load(s) and the battery. This component actually does the work of measuring power consumption. The final component of the test setup are the loads you wish to test. It’s important to make sure all the components in the setup are rated for the amount of current you expect to draw during testing. You can usually find that in the specifications of each individual component. You add those up and make sure your meter is rated for that much current and that your power supply can supply all of the required current. All the wiring in between should also be properly rated for that amount of current.
Example lighting current draw test
In this example I demonstrate testing a lighting device that runs on 12V and explain my methodology for hooking everything up and how I use back-of-the-napkin math to estimate power usage and requirements. In the above photo we have all three of our components for this specific test – a power source which is a battery in this case, the Powerwerx inline DC power meter, and load which is an LED lamp whose power usage I want to characterize. The Powerwerx inline meter supports a lot of measurements but in this post I’m going to mostly focus on current drawn and Ah, or amps per hour.
I started by connecting the power source to the “source” side of the power meter and then connected the load I wanted to test to the “load” side of the power meter. The images above show the light on but I will usually measure power with all the loads turned off to see if they draw current in the “off” position. It’s pretty common for devices to take a small amount of power even while off. This is called a parasitic load. The specific LED lamps I wanted to test have three settings: off, low, and high. I tested off and my power meter registered no current consumption. That’s probably because these lights have a hard off switch.
As you can see here this light draws 0.09A in the “low” position. If we were to run this device for 1 hour it would take 0.09Ah (amps per hour). You might have also noticed that there’s a measurement reading 0.001Ah. For this specific meter that means we’ve used 0.001Ah since the meter was connected to a load. There will be more on this measurement later.
With the LED lamp in the “high” position it’s drawing 0.35A of power. With the information gathered so far I can estimate how much power I’ll need if I want to run this light for a certain amount of time, and I can figure out how much power I can expect it to take while it’s running. If we use the Ah reading I mentioned earlier we can also understand how much battery capacity we’ve used since the last time the meter was restarted. Let’s start with that since I mentioned it.
To determine how much battery we’ve used as a percentage I’d use the following formulas:
battery capacity used as percentage = battery capacity / battery consumed
battery remaining as percentage = 100% – battery capacity used percentage
For a theoretical battery with 20AH of a capacity and 2Ah consumed the formula looks like:
20AH / 2Ah = 10% capacity used
100% – 10%= 90% capacity remaining
Now let’s add time to the mix. I’m going to use a Yaesu FTM-100D radio as an example of thinking about how much power it will use based on the specifications from the manual. According to its specifications when it’s receiving only it’ll draw 0.5A. The max power it will draw when transmitting 50W on 2m is 11A. Using this information let’s figure out how much battery we’d need to operate this radio some percentage of the time for 8 hours. For the purposes of this post we’ll call the amount of time we’re transmitting our duty cycle. We’ll assume we’ll be transmitting at 50W for 10% of the time that the radio is powered on. The formula will look like this:
Ah used = current * hours * duty cycle
While the radio is receiving only during an 8 hour operating period we’ll use 3.6Ah of battery capacity:
0.5A * 8h * .90 (90% receiving time) = 3.6 Ah capacity used
Now we should compute power usage when transmitting at 50W:
11A * 8h * .10 (10% transmitting time) = 8.8 Ah capacity used
Total power consumption over 8 hours for the radio:
3.6Ah (RX only) + 8.8Ah (TX at 50W) = 12.4Ah
When we add them up we need at least 12.4 AH of battery capacity to run that radio for 8 hours while transmitting 10% of the time. If you want to run the radio for 16 hours transmitting 10% of the time you’d either need to be able to re-charge that battery to replace the discharged power before the battery gets too low or have a battery large enough to run the radio for 16 hours, meaning you had at least 24.8 AH of battery capacity. There’s also a way to cheat on battery capacity. If you can reliably charge your battery as you run your radio from a source like a solar panel you can replace current that’s drawn down by your loads. In that case you’d just subtract the current you’re able to supply from your charging source from the load. If you end up with 0 or a negative amount of current draw you’re able to power your radio without discharging the battery.
Figuring out how much power you use as you go
This section can apply to both bench testing and operating in “the wild”. This details how you’d use any power meter that’s capable of measuring cumulative power use while you’re running loads. The Powerwerx meter I mentioned earlier and the BuddiPole PowerMini have this capability. If you connect one of these power meters inline with your setup as you operate and run loads it will add the cumulative power drawn. This can be useful when you want to understand how much power you’ve drawn down on a battery. As I write this before the 4/3/2022 Portland Neighborhood Emergency Team chat net and NET net I plan to operate on battery with lighting during the net and record my power usage here later, but the thing I do is the following for both bench testing and off grid measurements:
- Connect my power meter between the power source and load as described above
- Perform whatever activities I would normally perform
- When done I check the consumed Ah on the meter to get my battery capacity used
- Calculate battery percentage used
Formula for calculating battery capacity used:
battery capacity used / battery capacity = percentage capacity used
For an example with a 20AH battery and 15Ah of capacity used during some activity I would have 25% capacity remaining on the battery. I can use this formula in the lab to estimate how much power I’ll need in the field later, or understand how close I am to drawing my battery down in the field:
15Ah / 20AH = 75% used battery capacity
100% – 75% = 25% remaining battery capacity
Adding it all up
When you perform this kind of analysis on devices you expect to run off of battery in the field you can begin adding up all your field components and understanding what your power requirements will be. If you know your lighting will take 2Ah to run for a few hours at night and 12 hours of radio operation might cost 13.2Ah you can say your station will take 15.2Ah to operate for 12 hours. As you add more devices such as phone chargers, laptops, etc. your power requirements will change. You can also use this methodology to reduce power consumption. For example if running your radio at 5W is sufficient to achieve your communication goals you could save a lot of power, requiring a smaller battery, or less recharging capacity. You could also achieve similar results by having fewer devices or keeping your radio transmissions more brief (decreasing your duty cycle). Comparing the sums of power consumption between different setups can also help you inform either your expectations of how to operate or what is possible with the setup you have. It can also help you right-size a battery or recharging system for your specific uses.
A real-world example
I wanted to add an update with another example of operating the radio in reasonable conditions doing a specific task that isn’t entirely theoretical, or just on-the-bench testing. Tonight I was net control for the Portland Neighborhood Emergency Team chat net, and I also participated in the Portland NET net as well. For most of the nets I was running two LED lights and I topped the last 25% of my tablet’s power off. I ran my Kenwood TM-V71A at 5w which drew about 3A when transmitting and 0.55A receiving. Both of the LED lights were set on low and consumed 0.1A apiece. The charger’s power usage varied depending on the part of the charging cycle the tablet was in, but at the end of 3 hours of running the radio, and about 2 hours of running both lights I used a total of 3.42AH of battery capacity. The battery I was using has a rated capacity of 40AH, so I used about 8.6% of its capacity (3.42AH used / 40AH of battery capacity = 0.086) doing both nets and listening on the first net’s frequency for an hour before it began. The first net that I was transmitting more on used the majority of the capacity, about 2.3AH. During the second net I only used about 1.1AH because I spent the vast majority of it listening as we ran lights and the tablet charger.
Tying it all together
By the end of this blog post I hope you came away with a good understanding of how I approach understanding and estimating my power usage and right-sizing my equipment for specific uses. This approach also helps inform how I operate when I don’t expect to have reliable power or when my situation changes and I’m not able to recharge batteries, etc. It can also show you how big of a difference it can make when you transmit less or when you add or drop devices from your setup.
This pattern can potentially be applied to other equipment like medical devices that can be run on battery. I’ve used the same method to profile my partner’s CPAP machine’s power consumption with various settings. I’ve been able to determine what sort of battery and charging system that will be required to keep it running when grid power fails or is unavailable (hint: turning off the humidifier and tube heater really saves a lot of power).
Notes after the fact
On the advice of Kevin, N6KVN I’m going to add a note about batteries. While this bit of the post is a bit out of scope it’s important to touch of the strengths and limitations of various battery technologies. Some batteries can be damaged by discharging them to 50% and others can be discharged to 20% or possibly lower before damage occurs. It’s important to understand the characteristics of the equipment you’re running. If you’ve read other posts of mine you’ll notice that I field a lot of LiFePO4 batteries. One of the reasons (apart from weight and other safety factors) that I tend to use them is because they can be discharged to a depth of 20% of remaining capacity before they’re permanently damaged. Most common lead-acid battery tech (think car batteries) can only be discharged to 50% before permanent damage to the cells occurs, but they are much cheaper than lithium batteries. Comparisons of various battery types is an entire post of its own, but these things are worth mentioning as you size your system and plan for the amount of energy you expect to discharge or plan to use. As an example my 100AH battery really has a usable capacity of 80AH because if I were to discharge the battery to 20%, or 20AH it would cause permanent damage to the battery (100AH capacity * 20% limit = 20AH, 100AH capacity – 20AH limit = 80AH of discharge before damage). This information should be listed by the battery manufacturer. If it’s not included I’d recommend reaching out to their support team.
APRS test from Stone Tower in Montpelier, VT
During a small road trip through Montpelier and Burlington VT Jen and I decided to stop at Hubbard park to go for a walk and try some radio nerdery. I failed to get pictures on the beautiful snowy walk through the park, but it was wonderful and near sunset. I ended up trying to use my Yaesu VX-6R and Mobilinkd TNC3+ to send position reports, and was ultimately successful from the top of the tower we climbed.
As you can see from the screenshots above I was able to receive a bunch of stations from the tower and was able to get out a position report as well as some SMS messages via SMSGTE. Oddly I never got ACKs for my messages, but I did get a reply from SMSGTE as expected when using the “?” after the destination call. The previous messages were from tests.
As you see from the screenshots I did finally have some success sending messages from the VX-6R, but it’s not as reliable as I’d like. There’s some work left to go. As a side note I did eventually get some bi-directional messages going through SMSGTE that aren’t shown in this screenshot with Kevin, K7AJK. With enough elevation I was able to overcome the shortcomings of this setup. In the screenshots my call is K7JLX-15 and the icon I’m using is a red “X”.
Attempting HF QRP operation in NE VT
Howdy! This post is one that’s been in the drafts list for a hot minute, but I took a trip to NE VT to visit a partner and on valentine’s day we went out in the woods behind her place to radio for a couple hours. After a hike that seemed much longer up hill than down we arrived a higher spot with a clearing that would allow me to set the Superantenna up. I wanted to test my new Yaesu VX-6R with a Mobilinkd TNC3+ for APRS operation. I was hoping to make some contacts with Canadian stations since I was less than 1.5 miles from the border on the hike, but alas I don’t have something set up right.
To add a bit of fun the shoulder strap on the Superantenna bag failed as seen in the photo below as we hiked up. Unfortunately that meant we had to hand carry the unit up and back down.
After getting the setup ready to rock I tried some phone operations on 20m SSB, but was ultimately not able to make any contacts despite being able to hear a number of other stations. There was a contest going on so it was hard to reach other stations. I haven’t been having a lot of luck with the Superantenna lately apart from using for SWL. I kept the 4.5AH Bioenno battery wrapped in a warm shirt within my black Chrome bag to keep it as warm as possible rather than leaving it in the ammo can. I just ran the power cable out of the top of my bag and left it rolled up when we found the spot to set up. The only ill effect the cold seemed to have on the TX-500 was that the LCD screen was a touch slow to respond to changes, but I was able to tune to stations without issues. I was surprised not to see a bunch of frequency drift despite the weather.
I used the VX-6R with the Mobinlind TNC3+ in conjuction with a duplexer going to the Superantenna with a 2m load coil set up.
Superantenna and Chameleon Mil Whip 2 set up for 20m and 2m operation
In conclusion I made no contacts whatsoever and it was cold as hell, but it was a fun hike/bushwack and my winter gear held up very well against the cold. I’d like to try this again someday, but with the trail friendly 10/20/40m endfed. I also have more experimentation left to go to get my Mobilinkd TNC3+ working properly to do APRS. As a note it wasn’t nearly as difficult to deal with the Superantenna ground plane wires as I thought it might be. The main problem I had was that I’d wound them in a way that allowed them to get tangled up and deploying them was difficult. Rolling them back up wasn’t too difficult even when the sun was behind cloud cover.
Working ISS (01/23/2022)
This post is a bit of a quickie, but it covers an attempt to some of the basics about working ISS’ voice repeater and APRS digipeater. During this attempt to work ISS I wasn’t able to make any voice contacts, but I started with the following:
- An Android phone running ISS Detector Pro
- 5″ piece duct tape
- Yaesu FT3DR
- An Arrow handheld dual band 2m/70cm satellite antenna with built-in duplexer
Theory
As ISS or any satellite orbits earth in a non-geostationary orbit you’re likely to eventually have a certain number of passes over your location, depending on how the satellite is orbiting. You can use software to predict orbits, and therefore you can be ready when the satellite passes overhead. Ideally you’ll have the transponder frequencies of the satellite you’re trying to reach pre-programmed into your radio along with some doppler-shifted frequencies to try to reach the satellite as it approaches and departs. I didn’t do that, but have had decent luck without the doppler-shifted frequencies. Passes typically last minutes. What’s happening is that a lot of satellites have an uplink (ground -> space) and downlink (space-ground) frequency. Your radio must be able to transmit on one and listen to the other to make contacts. There are some cases where that’s not necessary such as working satellites with APRS digipeaters, or just receiving signals.
The attempt
I used the ISS detector pro app to find a longer pass (this one was about 6 minutes long). Before the pass I set my antenna up, connected it to my radio, and made sure it was in working order. After that I taped the phone to the beam of the antenna between the first 2m elements where it would fit using a piece of duct tape folded in on itself. Taping the phone to the boom enables me to aim the antenna using the app (screenshot later). I also configured the frequencies for the APRS digipeater on ISS, the crew communication uplink and downlink frequencies, and the FM repeater frequencies. As a side note sometimes astronauts, who are also licensed ham radio operators, will man the radios and talk with folks on the ground. In addition to programming frequencies you need to also program your APRS radio to use the digipeater path ARISS, otherwise the digipeater won’t send your packets back down to other stations.
Now it’s time for action! There’s a very narrow window to hit the ISS, so there’s a need to be quick and prepared. I went out in the street near my house a few minutes early with a clear-ish view of the sky and aimed the antenna at the satellite using the app. A screenshot below shows what the aiming screen looks like. The yellow circle is the direction the top of your phone is pointing and that should be aligned with the satellite on its track, the blue line with dots. The center of the screen is up and the and the outer ring is down. As the satellite passed I just aimed the antenna with the aid of the phone and tried to use the repeater. I didn’t hear anyone, but was able to switch to APRS and sent a beacon. I saw that the packet I sent was digipeated by ISS! Following that I checked the ARISS page and saw my call sign! You can also check https://aprs.fi and see your location as well as the path by which your packet arrived. The first hop for my position report was the ISS.
Camping in the Tillamook State Forest (1/21-23/2022)
It’s been a while and this will be a big post! My partner and I were able to go camping over the weekend, and if you’ve read any of my blog posts you won’t be surprised that I took the opportunity to practice some comms and off grid operating. I wanted to work HF, do some shortwave listening, and see if I could do any UHF/VHF communications. Additionally I wanted to run off of the 100AH battery box for a couple days to see how well it held up under constant use. This is also the first camping trip I brought the speaker stand antenna mast setup on.
On the way out I ran APRS with the Kenwood TM-D710G and the COMET-NCG CA-2X4SR antenna that mounts on the hood of the 4Runner. I noticed that on the way out that I had APRS coverage nearly the whole way out.
The first night we arrived late so I did a bit of SWL. I mostly got Radio Havana Cuba, Radio Nikkei, a distant station broadcasting in Mandarin, and Radio New Zealand International.
The next day I set the antenna up following a fun walk in the woods below the camp site. Most of my work on HF was done using the usual Endfedz Trail friendly 10/20/40m antenna. I strung it between the 4Runner and my portable antenna mast. I also added a 6m end fed dipole to the setup to see if I could reach Kevin, K7AJK from my camp site on the Lab599 TX-500. We had no luck. I wasn’t actually able to make any voice contacts on 20m with this setup even running at 10W, but there was a contest on the band so it was both congested and I suspect folks were running at fairly high power levels to make contacts. As you’ll be able to see from photographs I did a little hack with a stick I found to push the antenna higher off the ground on the truck side. It was especially helpful in preventing the hatch back from striking the antenna.
After a few hours of having no success running phone I decided to switch to packet. Moving the radio into the vehicle reduced the SWR and allowed me to run the entire setup from the 100AH battery since I had used the 4.5AH battery quite a bit for SWL already. I had also been simultaneously been running my 2m rig and APRSDroid on the tablet connected via Bluetooth to the mobile radio with a Mobilinkd TNC3+. I was able to send a number of text messages back and forth between friends using SMSGTE, which was nice given the complete lack of cell service. At this point I was still using the antenna on the truck.
After quite some time operating on digital I decided to test some configuration changes I made to js8cli to increase the accuracy of maidenhead coordinates I was submitting to APRS-IS via Internet-connected stations running JS8Call. I had some pretty good luck as my position was accurately reported.
Apart from all the fun I had on HF, and walking around the forest with my HT (where I was reliably digipeated at 5w) I also figured I’d try to see if I could hit some of the repeaters in the Portland area, so I swapped the vertical antenna on the vehicle for my collapsable J-pole and speaker stand antenna mast. Much to my surprise I was actually able to get into the repeaters in the Portland area at 5w, but it was a bit sketchy as sometimes they wouldn’t key up. Apart form that I could get a bunch of APRS stations and digipeaters as well as some folks on the 2m calling frequency. I actually ended up having much better luck on 2m than on HF this time around.
As you might have noticed from the pictures above I ended up moving the antenna because winds were getting higher and I was afraid the antenna might move side-to-side on the bumper’s tubing. I ended up shifting it toward the driver’s side where I could secure it to both the tube running horizontally and to the spot where the tube split, meaning the mast wouldn’t shift from side to size because it was secured with the paracord on both axes. since the antenna mount on the vehicle uses the same connector as most of my coax and the J-pole I was able to just connect the J-pole directly to the existing cabling in the 4Runner. Easy!
For the entire trip apart from doing some SWL with the TX-599 on its 4.5AH battery away from the truck and by the fire ring I ran all the lighting and radios from the 100AH battery box. We charged the tablet, my partner’s phone, and my phone from the battery box as well. We only drew down to 96% in two days. One day had a lot of heavy radio usage as well so that’s all a good sign.
Some witch’s butter we found on a stump near our camp site
Working portable from WY
Hello all, after leaving my last post in draft for a few months and not finishing it I figured I’d move right along and write another one! I had already set up my superantenna last night to do some SWL, but because the space weather is so good I decided to set up the Par EndFedz EFT-10/20/40 antenna to do some work on 20m. For today I used the arborist’s weight to hang the far end of the antenna in a tree in the back yard and connected the transformer end to the deck. The antenna was an estimated 20′ off the ground, and was oriented diagonally SE to NW across the yard. I had intended to run the antenna north to south but was unable to because the antenna was too long to be stretched from the deck to the right tree. I ended up moving it to another tree diagonally across the yard.
I made a partial contact with a Canadian ham out of Victoria, BC that suggested the solution to someone interfering with him was to “invoke the 2nd amendment” and solve the problem with a gun. Following that gem of a first partial contact of the day I decided to get off phone at that point and start operating JS8Call on 20m.
I connected the Raspberry Pi to the battery and Lab599 TX-500 and fired it all up. One of the first things I noticed was that the system clock was wrong. After using “timedatectl status” I saw that my hardware clock was right but on boot it failed to update the system clock. At that point I did it manually (“sudo hwclock –hctosys”). Since I had connected the Pi to the wifi at the house the previous night to run updates I was able to set my tablet up in the kitchen and leave the radio outside while I operated as there wasn’t enough cable to bring the radio inside. The family was around inside and it was considerably warmer in the house than it was outside so I could make QSOs and still talk with everyone that was inside. That’s one of the nice things about using keyboards and a slower mode like JS8Call – you can still talk with people while messages are being sent and received.
I made a few contacts but had a nice long QSO with W7SUA in AZ. Apart from that I was getting two way communications with stations over 1,800 miles away though they were generally automated requests for signal reports and locations.
Bench testing 100Ah battery box improvements
With a potential COVID-19 exposure I decided to work outside in order keep my housemates’ exposure as low as possible. This afforded me the perfect opportunity to test running a high performance laptop from my batery bank and on solar power. I wanted to bench test integrating a West Mountain Radio Epic PWRGate into the existing battery box that had been intentionally designed without and integrated charger. The first and second days of the test with good and poor sunlight respectively went well. The solar panels were holding the battery up and by the time I was done working the battery was fully charged. It is worth noting that earlier in the morning the laptop was running on the battery, but as the sun came up the battery began recharging in both cases. Of course the battery charged more slowly and sometimes went into a discharging state on the cloudy day but ultiately all the power drawn from the battery was replentished.
I added three new Powerpole ports to support the installation of a West Mountain Radio Epic PWRGate for use as a multisource battery charger and to allow one port on the battery box to function as a UPS, one as a DC charging input from a vehicle or other 12v power supply, and a solar panel input that can work with lower voltage (<30V) solar panels. I also added a charger disconnect switch that prevents the charger from acting as a parasitic load when it’s not in use. The specific disconnect switch I added allows the red rotary part of the swtich to be removed n the event you want to make sure the charger isn’t connected to the battery by mistake.
The Epic PWRGate connects to the ports with 10GA stranded copper wire to support 30 amp loads. The “battery” port on the PWRGate is connected to the battery via the DC disconnect switch and the DC subpanel. The leg of the circuit that connects the battery to the charger is also fused with a 30A fuse to allow it to operate a full power radio via the UPS port. The Epic PWRGate will charge a battery with a max current of 10A. I also added an optional temperature probe connected to the positive battery lug that will cut the charger off when the battery gets too cold or warm to prevent harm to the battery. The temperature parameters are configurable using the USB port. The appropriate USB cable, USB C, and USB A OTG cable adapters are included to connect a device with a serial terminal emulator installed.
This updated simplified build diagram for the 100Ah battery box includes the modifications that were being bench tested and will likely remain as a permanent addition to the system for charging from a vehicle or charging from a lower voltage (<30v) portable solar panel.
As a side note an added advantage of including a charger like the Epic PWRGate to this setup is that it can be re-configured to charge another battery, even of a different chemistry from the 100Ah LiFePO4 battery. You can charge a smaller battery or even charge a lead acid battery from it as well. This will require changing jumpers if you’re not programming the unit with a USB port, but I prefer programming it with a USB port as I get a better degree of control over the settings such as charge current than the onboard jumpers provide. It will also require swapping the battery and DC ports. The battery should be connected to the DC port and the DC port should be connected to the battery being charged. In the event the charger is re-configured I also include the custom LiFePO4 battery settings for my Relion RB100 that the kit is designed around so they can be restored on the charger without requiring memorization.
I also ended up having shading issues in the space that was available to set up the solar panels so I used the built-in eyelets and some paracord to suspend the panel in the sun to avoid shading on the ground. I was also able to slide the panel laterally on one piece of cord running left to right (east to west) near the water tank pictured. The other piece of paracord goes through both of the eyelets and forms a tiangle whose point is a knot and the single line of paracord runs back to a single anchor point from the triangle, and is pointed south. You can slide the panel side to side on the paracord running right to left (east to west) as the sun’s position in the sky changes. Getting the panel off the ground was extremely helpful because it got the system out of shadows cast accross the ground most of the day, and also required less maintenance as shadows tracked across the ground and threatened to partially or fully shade the solar panels. Instead the shadows were cast under the suspended panel.
The 100W folding panel was able to charge both a 19″ Macbook Pro connected to a 90W USB C car charger and a phone the an entire work day. This worked well on a bright day and on a cloudy day using this new configuration. I leverage MC4 connectors for the 100W panel to harden the connections against rain and dust. They’re adapted to Anderson Powerpole connectors for connection to the battery box using a pigtail I store in a zippered pouch on the back of the folding panel along with rolled lengths of wire with MC4 connectors attached.
This is an update to this post about building the battery box.
Using the portable LiFePO4 battery banks in the Gifford Pinchot National Forest
This won’t really be a post about doing a lot of operating. It’s mostly about powering and recharging stuff. The long story short of operating from the specific site we were at is that I didn’t make any contacts apart from another station on JS8Call that heard one of my heartbeats. I wasn’t in a good position to be heard, but I could hear a lot of other stations on 40m throughout the afternoon and evening. I was also able to hear Radio Havana and what I suspect might have been Zambia NBC Radio 1 for a few minutes.
I was able to recharge the Bioenno 4.5Ah battery in an hour or so as we broke camp and packed the vehicle. I’d been using that radio the previous day and listening to shortwave stations the whole night. A solid hour of charging at 1.1A using the BuddiPole PowerMini on a single GoalZero Nomad 20 solar panel was enough to replentish the battery.
The 100Ah battery was easily charged in about 45 minutes. We’d only drawn about 3.5Ah from the battery running lights, charging a phone, and a portable projector. The panel in use here is a Bioenno 100W folding panel and from the VictronConnect application screenshot it’s charging at about 4.5A. The back view shows how the solar panel is connected to the charging unit and the battery. This is the first time I’ve used the West Mountain Radio Epic PWRGate to charge the 100Ah battery. I’m hoping to use it for charging from a vehicle alternator, an existing DC power supply, or solar panel. I’m also hoping to add a charger like this to the box along with a temperature probe to ensure the battery isn’t charged when it’s too hot or cold. The Relion RB100 has a minimum charging temperature of -4F.
This a detailed view of the West Mountain Radio Epic PWRGate. The green LED indicates it has good solar charging voltage, and the blue LED that was slowly pulsing which indicated that the battery was being bulk charged by the solar panel. The PWRGate is programmed with the specific battery chemistry settings for LiFePO4 batteries and is current limited at 6A for some of the other batteries I charge with this setup.
