Welcome to the Off-Grid Ham Shack series. In this series we go through putting together a solar-powered off-grid ham radio station (Ham Shack). This article covers everything from solar panels, charge controllers, power distribution, and battery storage capable of powering our communications gear for fun, or in a grid-down scenario.

UPDATED 09 11 March 2024

Breakdown of an off-grid ham shack

Just like our portable ham radio stations, an off-grid ham shack starts with generating and storing energy. That energy can come from a solar panel, hand-crank generator, wind turbine, or some other DC source. In order to keep things simple, we will focus on a solar powered ham shack.

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Solar panels

The solar panels we use for fixed installations are much more cost-effective than the portable panels we’ve seen on the channel and blog previously. This makes our fixed off-grid installation more “budget-friendly”, compared to the lightweight, man-portable options we use in the field.

Ultimately, deciding which type of solar panel is right for you, isn’t something someone else can do for you. For the off-grid ham shack, I chose 5x Renogy 100-watt rigid panels as the core of the solar panel system. These were chosen for being well-designed, having a great warranty, and cheap delivery costs. I decided on a larger number of smaller panels for redundancy, versus a fewer number of larger panels, with little or no redundancy at all.

Solar charge controller

Since charge controllers are not all the same, don’t be tempted to rush out and buy a cheap rebranded charge controller! A solar charge controller acts as a gatekeeper for your solar storage system. It insures our batteries are optimally charged, protected from overcharging, deep discharging, and maximizing the overall efficiency of our battery storage system. Your charge controller should do all this, while being RF quiet! This means they shouldn’t create noise in your radio equipment.

The solar charge controller is the first and last defense in protecting our battery. Here’s how:

1. Current Regulation: When sunlight hits the solar panels, the panel will generate direct current (DC) electricity. The charge controller helps regulate (or limit) the amount of current from the panels to the batteries. It ensures that the batteries receive the appropriate charging current, preventing the battery from being overcharged, or charged at too high current.
2. Battery Protection: Solar charge controllers monitor the battery voltage. The charge controller will alow charging when the battery voltage is within certain voltage limits. It will also prevent charging of the battery, if the battery is full. These features help protect the battery from excessive discharge, and inadvertently oversharging our battery. Both scenarios can lead to damage or reduced battery life.
3. Preventing Overcharging: As mentioned above, overcharging can damage the batteries and reduce their lifespan. Solar charge controllers use a technique called pulse width modulation (PWM) or maximum power point tracking (MPPT) to prevent overcharging. PWM controllers (Bad!) regulate the charging voltage by pulsing the current flow to the batteries, while MPPT controllers optimize the solar panel’s output voltage to deliver maximum power and adjust the charging parameters accordingly.

Battery storage

In an off-grid solar system, a battery acts as a reservoir, storing the energy produced by the solar panels for later use. This stored energy can power our electrical devices when the sun is not shining, or provide additional current when current from the solar panels is insufficient. Without a battery, the solar energy generated during the day would be wasted, since it cannot be stored without one. Therefore, a battery ensures continuous and uninterrupted solar storage, in off-grid solar systems.

One question coming in is “Can we power our radio equipment directly from the solar panels?”. In theory yes! This will work fine until a cloud passes between the solar panel and sun. If your equipment takes more current than your solar panels are producing, your station will get shut down! Try to run the station at night, it’ll get shut down! If you are running a low power station, on a clear sunny day when the sun is fully illuminating your panels, sure it will work fine, within the caveats mentioned. The thing is, the battery provides a buffer between your station and solar panels. No sun, no problem, the battery will take over.

For LiFePO4 cells, the efficiency of the charge and discharge rate is also very high – above 97% or more. That is why the Peukert’s exponent is close to 1.00, meaning LiFePO4 batteries don’t suffer from Peukerts law as lead-acid batteries do. Peukert’s Law, named after the German scientist Wilhelm Peukert, is a mathematical equation that relates the capacity of a battery to its rate of discharge. It states that the actual capacity of a battery decreases as the discharge rate (load) increases. In other words, the higher the current draw from a battery, the lower its effective capacity will become.

Battery Expansion

There are times when we want to add additional battery storage to our off-grid ham radio station. Although this is a simple process, there are some things to watch out for when connecting batteries in parallel. Here are a few tips:

• Never connect an old battery with a new battery.
• Always use batteries with identical voltage and capacity.
• Never connect batteries with a high voltage mismatch.
• Never connect batteries of different chemetries.

Power Distribution

Power distribution is a crucial aspect in of any off-grid ham shack. Power distribution takes a single DC connection or port, dividing it into multiple DC ports. The primary objective of power distribution is ensuring that the supplied connections are appropriately distributed to multiple devices or components within the system. By dividing a single DC connection from our battery storage, into multiple DC ports, it becomes possible to power multiple devices simultaneously. In regards to the off-grid ham shack, think multiple radios, computer, lighting, desktop cradle charger, … all powered through power distribution. Keep in mind, power distribution does not divide the voltage or current in the system. It is up to you to use a battery capable of providing the necessary voltage and current for the load placed on your storage by the peripherals. If you draw too much current with your peripherals, your voltage will drop! Test and measure your constant loads on your system.

I chose the Windcamp AP-8, 8 Port 40A power distribution board. It has one fused DC input, and 7x fused DC outputs. I decided on the 40 amp Windcamp AP-8 because my station will never approach the 40 amps limit for any reason. Generally, with all my radios transmitting simultaneously, the maximum current load on my battery storage is ~25 amps. With one port reserved as the primary input port @40 amps, the other 7 ports are divided by maximum potential current from the equipment connected to that port (up to 40 amps).

Wind Generator

Building a Solar Powered Ham Radio Station

Other considerations

AC (Alternating current) or DC (Direct Current) Ham Shack?

DC electricity, short for Direct Current electricity, is a type of electrical current that flows in one direction. In a DC circuit, the flow of electric charge remains constant, maintaining a constant polarity. This means that the positive and negative poles of the circuit always preserve their respective charges. DC electricity is commonly produced by sources such as batteries, solar cells, or DC power supplies, DC electricity is widely used in various applications, including electronics, telecommunications, and automotive electrical systems.

Most ham radio equipment runs on DC electricity. In fact, most mobile ham gear will operate from a range of voltages between ~12 to 15 volts. Often, portable ham gear generally operates on voltage ranging from ~9 to 16 volts. Green radios (surplus military radios) generally operate on a range of voltages ~9 to 24 volts. In the ham shack, it is important to keep our gear DC whenever possible. The target range for most ham radio gear is ~13.8 volts. Some operators mistakenly believe a slightly lower or higher voltage will negatively impact the performance of their radio. This is usually a matter of individual perspective, as most gear is designed to operate throughout a voltage range, rather than one specific voltage. What is important is providing a reliable DC output for our ham radio gear. More on this later.

For now, try to focus on keeping your ham shack ~13.8 volt DC compatible!

12 volt, 24 volt, 48 volt, battery & solar?

There are often reasons some Operators might want to run higher voltage solar or batteries. Usually, there is other non-radio equipment like DC to AC inverters, which could benefit from the higher voltages and thus, operate more efficiently. There is also the point of increasing voltage to reduce current which allows for reduced wire size between solar panels and the battery. Keep in mind when we run higher voltages, we also need to drop that voltage back down to something our radio gear can use. This process can (but may not) introduce noise into the system.

For example, one of my solar strings had 3x 100-watt panels in series. The charge controller takes that 60-70 volts from the solar panels, dropping it down to 14.4 volts for battery charging. Although this creates an excellent charging environment (in spring & summer), it also creates and an enormous amount of RFI noise during the bucking process of reducing the voltage. That noise prevents an Operator from hearing his/her radio spectrum effectively. This is unacceptable if the primary role of the station is communications.

(18 December 2023)I have replaced the 3x 100-watt solar panels in series, with a combination of 3x 100-watt solar panels in parallel. There are two benefits to this. Firstly, the panels in parallel seem to work much better near the winter solstice (no direct sunlight) than 3x in series configuration. Second, there is little if any RFI from the bucking process of the charge controller. I understood this would mean replacing the wire between the charge controllers and solar panels with heavier gauge, but the reduction in RF noise was worth the configuration change.

This is a topic we’ll need to discuss in more detail later on.

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With the basics out of the way, the following video will make a lot more sense to newcomers to this topic. After watching, if you want to go down the rabbit hole, keep on reading from the section underneath this video.

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OH8STN Ham Shack

From here on down, the discussion becomes more abstract.

Overview

The charge controllers are connected to the 2x 100ah LiFePO4 battery packs in parallel. Each charge controller is fed by one of the multiple strings of solar panels. The strings provide redundancy to the overall system. More on redundancy later.
By the way, the Victron 75/15 MPPT has been removed from the system. Good riddance!

Most of my solar panels are oriented vertically. This is to maximize the collection of solar energy during winter months at 65° North. During spring, summer and mid-way through autumn, there is a near abundance of sunlight at this latitude. For this reason, summertime “optimal” solar panel orientation is unnecessary in such a solar-rich environment.

Solar storage

Ultimately, the station will receive 4x 100 amp-hour batteries 5120 watt-hours in parallel. With radio equipment, lights, power for the diesel heater, computers, … 5.12Kwh is more battery storage than the station will ever need for any scenario.

Charging & Redundancy

The station uses several strings of solar panels connected via multiple charge controllers. Each charge controller is connected to a unique solar string, wind turbine or hand-crank generator. There are also spare charge controllers for adding supplemental DC sources. We’ll discuss supplemental DC inputs a little later.

The following short video shows the energy flows from solar panels, to energy storage, to consumption. Each step in the chain has built-in redundancy.

This solar panel and charge controller configuration adds redundancy to my off-grid energy system. Each solar string can feed energy to my main solar storage, independent of the other solar strings. In fact, as long as at least one string of solar panels remains, the system will continue recharging itself from solar power (albeit slower).

This is also true for the array of parallel charge controllers. Each charge controller is responsible for a single string of solar panels. A damaged or destroyed solar panel does not affect the charge controller, as the charge controller will switch into a “fault” state to save itself. If there is a short circuit between the charge controller and battery, a fuse will blow, disconnecting the charge controller from the solar storage.

There are also secondary solar storage systems in place. For example, the EcoFlow River 2 Max is fed by the 2x Power Queen 100ah LiFePO4 batteries when voltage is above 14 volts. In a pinch, the EcoFlow River 2 Max can power the Off-Grid Ham Shack in QRP mode, for up to 3 days without recharging from solar. This provides a redundant power source for the comms gear, lighting, … if something were to go wrong with the PQ 100ah LiFePO4.

There are also several DIY LiFePO4 batteries of various sizes. These are trickle charged from a 60 watt PowerFilm Rollable panel and Genasun controller. Their only role is to be ready to go if an additional power supply is required somewhere else, for some other purpose.

Radio equipment & services

My station runs several services for the benefit of my group and community. Some of these services allow local Operators and those around the world, to connect to one another for keyboard to keyboard chat, messaging, and the occasional rag chew. These services also allow Operators to reach out to others far beyond their own station’s direct capabilities, receiving advice or experience with topics outside their primary skillset. The interaction can very well be a two-way exchange of expertise or even a lifeline.

Services running on the off-grid ham shack

• Winlink gateways on HF & VHF
• JS8Call station 24/7
• Robust Packet (HF APRS)

Dual-band VHF/UHF charging

The ecoFlow River 2 Max is fed by the 100ah Power Queen Lithium Iron Phosphate battery which power my shack. This offers an amazing level of redundancy, the station has not had previously.

For the dual-band VHF/UHF radios carried in my chest pack, it is critical to have them powered up and ready to go at a moments notice. Since they live in the ham shack when not in use, charging in and out of the shack should be simple and easy.

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Efficiency & current consumption

When running off-grid and/or generating our own energy, it is important to keep the current consumption as low as possible while maintaining effective communications. Doing so allows us to extend the operating time of our stations, without an unnecessarily large energy collection and storage system.

What this really means is keeping each part of the station as efficient as possible. For example

• No lossy antenna – Always use a resonant antenna when possible!
• Ultra-low current consumption radios – 300ma or less on RX is good.
• Ultra-low current consumption computer or tablet
• Ultra-low current consumption LED lighting

For the most part, my off-grid ham radio station utilizes energy-efficient portable ham radio gear. The reason is “low current consumption“. While many operators look at radios like the Icom IC-7300, Yaesu FT-991A or similar, these radios have a very high current consumption, while doing nothing more than receiving! The higher the RX current consumption, the larger and more expansive our solar collection and solar storage needs become. As a rule, our current consumption goal should not exceed ~350ma on RX. Current consumption more than 500ma on RX, can become a complete no-go for sustainable off-grid or grid-down communications. It is not impossible to sustain more tan 500ma on RX, but can become costly to do so, the further one lives from the equator. The bottom line is: The more current our station uses while idling, the more solar panels and battery storage required to keep the station running off-grid.

The average RX current consumption of QRO (high power) radios is 1-2 amps. This is not a problem in a vehicle, where the engine is also our power supply. On the flip side, energy efficient QRP rigs and potentially amplifiers to augment them come in at a much higher price than their QRO counterparts. However, QRP rigs have a much lower current consumption than ORO radios. The trade-off is we can get away with smaller, less costly solar and battery storage to power them in the shack. QRO rigs are often (initially) more cost-effective to buy, but require a larger off-grid power supply to keep those stations running grid-down. It’s the old bait and switch!

Why not just reduce TX power!?

RX current consumption isn’t the only concern. QRO radios are also less efficient on transmission. Take for example my Icom IC-705 and DIY599 PA500E amplifier. Total current consumption on RX is less than 300ma. Total current draw at 100 watts is ~12 amps. As an example, RX current consumption of my old Yaesu FT-891 on RX was ~1.2 amps. On TX the FT-891 at 100 watts consumed 20-22 amps. Do you see where we are going with this? Off-grid comms is not about buying popular gear. Rather, it is about energy efficiency! Every green radio ever produced follows a “more efficient” methodology. If this fact is overlooked, our comms gear will sit quietly in the corner because we didn’t build an energy efficient system, to power it effectively. Let that sink in.

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Supplemental solar generation & storage

In total, the off-grid ham shack has ~5312 watt-hours of LiFePO4 solar storage available for any grid-down scenario, encroaching upon our community. That is 3072 watt-hours of primary online battery storage, with the rest in reserve. Moreover, the off-grid ham shack has 740 watts of primary online solar panels, AND an additional 3055 watts of supplemental, field deployable solar power on reserve. Along with reserve radio gear, additional solar storage and rapidly deployable solar panels, these are stored in EMP hardened hard cases, in case the unthinkable happens.

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Every time I publish a video on off-grid solar power, someone comes along a says “WIll Prouce” says bla bla bla. Will is incredible, and I watch his channel myself. The thing is, Will focuses on energy for the RV, the cabin, the van, the workshop, and even the home. Most people don’t/won’t understand the red flag here but here it comes. Those systems generally use inverters and higher voltage. They have higher voltage solar arrays, higher voltage batteries (if they have batteries at all). The problem here is most radio communications gear runs on 12-15 volts of DC power. This means we will need an inverter to convert xxx volts AC to power a DC power supply outputting 12-15 volts for our radio equipment. This method has lots of losses. Losses eat up our battery storage unnecessarily. So, the red flag is the inverter! Inverters are also notoriously noisy to radio communications gear. Because of this we MUST/SHOULD keep our off-grid comms power DC (whenever possible), in a voltage operating range of ~12-15 volts or ~9-16 volts for portable gear. This removes the need for any micro inverters at our solar panels, or inverters after our batteries powering the AC power supplies to power our communications gear. Don’t run comms gear off AC inverters!

This doesn’t mean we can’t have a hybrid system using inverters for some other purpose eg my air compressors, someone’s CPAP machine, or even to power an off-grid refrigerator or freezer. One of the reasons for the EcoFlow River 2 Max in the off-grid ham shack is its AC inverters. Normally these inverters are disabled. If for some reason and AC device needs to be powered up in an emergency, the EcoFlow River 2 Max can handle that job. Otherwise, the inverters are off, and not bothering anything. This page assumes your primary goal is powering your ham radio station off-grid! If you want to run an air-conditioner on solar power, this may not be the right place for you. Food for thought!

Heating the ham shack in winter

One overlooked aspect of a sustainable ham radio station is how it will be heated. In cold weather regions, heating in winter can make or break any off-grid station strategy, For my off-grid ham shack, the operating space, the operator, and the lithium batteries need to be kept above freezing.

The lithium iron phosphate batteries we use in our ham radio stations, often come with a temperature spec which states a charging range starting above freezing. Operators can function below freezing, but would certainly be more comfortable in a more mild climate.With that said, here is how I keep the ham shack and its lithium batteries warm in he harshest winter weather:

Recommended Gear

Power Queen LiFePO4

Power Queen provided the first 100ah LiFePO4 battery for the off-grid ham shack project. At the time of this writing, the first one has been in use for about ~5 months (August 2023). Naturally it will take years for a long term review of the battery, but so far so good. If something bad happens, you’ll get a new video from me pointing out the failure. Based on the performance so far, I may purchase several more of these packs for a total of 400 amp hours of active solar storage for the off-grid ham radio station.

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Genasun Controllers

The Genasun GV10L controllers are the most RF quiet controllers I’ve tested so far. They have been demonstrated on the channel from the beginning. I do understand they are not the most cost-effective solution for multiple strings of solar, but they are RF quiet and robust. Despite the marketing from companies comparing themselves to Genasun, Genasun controllers remain a pillar in my portable operations and ham shack off-grid power strategy.

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EcoFlow River 2 Max

For other regions around the world, please check out your local EcoFlow distributor.

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Windcamp Power Distribution

We’ve already discussed power disribution earlier in this post. Power distribution allows us to split a single DC output to multiple DC output ports. I chose rhe WIndcamp AP-8 40 amp power distribution board. Its been about a year since purchasing the first one. I have no regrets.

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Winter charging tips

Charging is challenging in any Northern latitude. Moreso as we get closer to Arctic regions. At the time of this posts publishing, I can recharge the 100ah Power Queen battery to about 90% full each day, provided there is no sleet or snowfall. During November, December and January, we have just a few hours of day light. This can be enough if our solar panels remain clean, and we keep our current consumption as low as possible while maintaining effective communications. From the beginning of Decembr until the end of January, the days are so short there is little point in making the effort to charge from solar. If something comes in, I’ll take it. Still, I won’t be holding my breath.

Here are a few tips I use to maximize solar collection during winter season.

• Reduce your current consumption!
• Vertically mounted solar panels will keep you orienteed at the winter sun, which is generally low in the sky.
• Use additional strings of solar panels to capture sunlight, throughout the day.
• Genasun boost controllers help in low light. Here’s how:
  1. We can use them to boost voltage from a panel with putting out lower voltage (dark days).
  2. We can use them with solar panels running higher voltage in series-parallel, then buck the voltage down to the battery charge voltage.
  Either way, the charge controller will manage the voltage boost or buck to keep charging happening, when it would otherwise be off.
• Whatever solar panels you think you need, double or triple them as you build your station.

Grid-Down Power for disasters

Grid Down power for communications is very often overlooked in the community. We tend to approach radio communications from a hobbyist perspective, meaning it is non-critical. I created this video some years ago to give Operators an idea of grid-down communications during a disaster. There has been many examples of disasters affecting grid-tied electricity. Our ability to power up our stations using our own power is something every station owner would aspire to achieve.

Off-grid power for emergency communications is the single most overlooked aspect of survival radio today. Whether you’re sporting a Baofeng UV-5R, a fancy DMR radio with 256bit AES encryption, or the latest greatest Yaesu FTDX-9000X, they all need a reliable source of energy to operate grid-down.
The following video goes through my off-grid power plan. The plan is focused on autonomous energy collection, energy storage, and energy distribution. The plan is robust, redundant, and adaptable. There are no single points of failure, and each component has a backup candidate, if any single part of the system fails.

Quite often, portable stations, mobile stations or otherwise low-power stations find themselves reliant upon repeaters, Winlink gateways, and APRS Digipeaters, … Like Pavlov’s dogs, we have been trained to believe these types of “open” systems have an unlimited off-grid and redundant power supplies keeping these services up. There is no guarantee these stations will remain endlessly powered up during a grid-down scenario. Many of these critical services are operated by advanced Operators just like you or me. The cost of maintenance is already high, without adding on the expense of a completely off-grid and/or redundant power supply, capable of running that station in the worst of times. Because of this, we need to change the way we think. Rather than being dependent consumers of off-site services, we must:

• Become more grid-independent and energy self-reliant.
• Learn to communicate station to station, without “middle-man” stations in-between.
• Deploy our own off-grid services Eg fill-in repeaters, Winlink Gateways, JS8Call & VARAC stations, …

Take this seriously. The singl biggest mistake new operators make is beleiving that repeater will be operational during a grid-down disaster.

Previous battery & power videos

In previous years, I have proposed having a power system specifically for our communications gear. That philosophy hasn’t changed! In fact, I believe it is even more important as the escalation of global tensions and beginning of end times arrives. These signs make formidable arguments for independent energy sources in the “post-pandemic” world. Yes, the world we live in has become much more dangerous. I long for the days when an earthquake, tornado, hurricane or nor’easter were the most likely scenarios to ruin our day. Please take off-grid power seriously!

Related Posts

Building a solar-powered Off-Grid Ham Radio Station for beginners
https://oh8stn.org/blog/2023/12/21/building-an-off-grid-solar-powered-ham-shack/

Radio friendly MPPT charge controller:
https://oh8stn.org/blog/2023/11/30/radio-friendly-mppt-charge-controller-for-off-grid-comms-genasun/

Current consumption and off-grid communications
https://oh8stn.org/blog/2023/11/20/off-grid-grid-down-comms-current-consumption/

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73
Julian oh8stn
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