Tag: DIY

Bench testing 100Ah battery box improvements

Bench test, Not actually radio related
Battery box sitting on a concret slab with wires running from it.
Battery box with solar power and a 90W USB charger connected via a PWRNode
Zoomed out view of the battery box with a wire running to it from the right that's taped down, a laptop on a bench near the battery box with wires running into it from the battery box.
A wider view of the work area with the solar cable taped to the ground and the laptop on a workbench

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.

Two powerpole ports populated with power cables on the power box's side.
The added solar (left) and UPS (right) powerpole connectors
View of closed powerpole ports, two populated powerpole ports, and a red disconnect switch as seen from the corner of the battery box.
The existing 30A charging port (top), added disconnect swtich for the charger (middle), and added DC in port (bottom)

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.

Open battery box revealing connections between internal components including the Epic PWRGate.
Opened battery box with the Epic PWRGate connected for testing

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.

Block diagram of 100Ah battery box

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.

Solar panel suspended from paracord in the sun.
Suspended foldable solar panel

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.

Coping with the heat wave

Howto, Not actually radio related, Stories, Theory

Hello all, while this isn’t actually a post about amateur radio I wanted to post about how we (my partner and I) decided to deal with the June 2021 heatwave in the Pacific Northwest. While this isn’t directly related to ham radio I think it’s worth discussing as the temperatures in this region don’t typically reach the levels they were at and most homes and people aren’t prepared to cope with those temperatures. Some folks will probably laugh at this post and the situation in its entirety, but you have to remember that homes, businesses, animals, and people in what is typically a fairly temperate climate aren’t used to these sorts of temperature spikes. Some of us will mostly be uncomfortable and maybe inconvenienced but for others this is a deadly situation. There are large numbers of unhoused folks sleeping rough and stuck outdoors during this time. It is easy to die of exposure in situations like this even in a city. In nature you might be better or worse off depending on where you are. When operating in the field it’s important to keep yourself and your equipment cool, and I don’t think this is the last time we will have unseasonably hot weather. Next time it could be during another disaster or trigger secondary problems like power outages. This post is mostly about optimizing a solution for a problem with cheap and easily available materials to decrease misery and help alleviate a situation that could lead to an emergency.

One obvious issue with the house we live in during this specific situation is that it has a very large single-paned south-facing window, which definitely heats the house up during the summer. We were fortunate enough to have a single window-mounted AC unit for the whole house but it was only able to keep the house in the high 80s to low 90s which is definitely better than 110+ degrees, but I wasn’t sure if the power grid would hold up under additional load and the heat itself. My partner and I decided we’d take some steps to cool the house further for our comfort and our dog’s safety. The most obvious thing we could do to limit solar gain would be to cover windows that we could with blankets, etc. which helped, but we didn’t have a big enough blanket to cover the window. I wanted to actually keep the heat outside rather than heating a blanket that was already on the inside of the house and having it radiate that heat into the living space. A cheap reflective shield with an air gap between the shield and the house would be a possible solution to the problem.

Problems to solve:

  • Keeping as much heat out of the house as possible
  • Shielding a large area
  • Keeping it simple
  • Passive cooling (a plus)
  • Temporary mounting
  • Not wanting to put tape on paint
  • Keeping it cheap
View of the outside of a house with a mylar blanket suspended in front of a large window supported by paracord. There are lots of plants.
Hastily constructed mylar “heat shield”

A quick trip to the grocery store yielded the following materials: a roll of duct tape, 50′ of paracord, and 4 mylar blankets (we only needed 3 it turns out). The entire solution cost less than $20, some moderate burns, and sweat. We taped the edges of the mylar blankets on both sides to hold them together and taped across the gap intentionally leaving holes that would be left to ensure the wind loading was lower since this was in part just held up by tape. Our first attempt at the solution was to run paracord from the fence to the gutter, but it required too much paracord and the angle the mylar blanket would be at would be less-than-optimal so I ran the paracord from the ground and weighed the ground ends and center point down with rocks. The end of the paracord attached to the gutter was run between the gutter nails and didn’t require tying or taping. I did, however, end up taping the corner of the mylar blanket to the inside of the rain gutter because there wasn’t a suitable anchor point for paracord near the corner of the house that I wanted to cover. We weighed down one corner with some rocks and were back inside within 35 minutes. Ouch note: ladders get hot in intense sun and gloves are a good idea.

The photos I’m including were taken after day 2. We had to go back out and shore parts of the heat shield up because some of the spots I taped to the paracord slid down. To combat that I just did extra-long wraps of duct tape around the paracord and attached it to the edges of the mylar blankets. I also taped the inside of the shield to the paracord at the bottom to prevent the heat shield from riding up the paracord. The end of the mylar blanket that was weighed down by rocks also tore in the wind/breeze so we coated the corner we stuck the rocks in with duct tape as a protective pad for the mylar. All the photos are this setup are shown below. The air gap between the window and mylar also served as a nice passive cooler. As the breeze and wind blew between the mylar and window it carried some of the heat away. After installing the mylar heat shield the temperature in the house dropped by 10-15 degrees over the next 30 minutes!

View from the inside of the window showing hanging plants, art work, and the mylar heat shield. Paracord is duct taped to the blakent to keep it off of the window and in position.
View of the back of the heat shield through the window.
One corner of a mylar blanket duct taped to the inside of a rain gutter. The tape is coming off the gutter in spots and the blanket is precariously attached.
Duct taped corner two days after installation. This is the weakest part of the installation.
Paracord tied around two rocks being used as a center point anchor with two "wings" going two directions. Mint and raspberry plants are behind the rocks.
Rocks anchoring the center point of the paracord running from the ground to the gutter. Both ends of the paracord were held down by rocks as well.
One corner of a mylar blanket being covered in duct tape and weighed down by three pieces of broken concrete sitting on a piece of wood in front of some siding.
The duct tape re-enforced corner of the mylar blanket is held down with broken concrete.

Pros:

  • Cheap materials that are readily available
  • Relatively fast to set up on the fly
  • Minimal tooling required to put it up
  • Removable
  • No tape used where it could remove paint
  • Effective at reducing temperature and quickly

Cons:

  • One-time use
  • Will require cutting to get it down
  • Required some maintenance after a day of being up
  • Needs a ladder to set up
  • Required two people to be outside in the heat on the south face of the house for 35 minutes
  • Kinda ugly
  • Dealing with duct tape on top of a ladder in wind wearing gloves is a PITA

Lessons learned

  • I burned myself on the ladder before getting gloves. Don’t get burned.
  • I got sunburned, but when I sweat it dissolves sunscreen so that was expected.
  • I should build something prettier ahead of time that’s easy to take up and down but also cheap to build.
  • Putting a ladder in the middle of a garden bed without absolutely destroying the (very thorny) plants is hard but doable.
  • The mylar blankets in this configuration worked very well!