In the world of portable radio operators and emergency communicators, staying connected is not just a convenience—it's often a matter of safety and mission success. Whether you're out in a field training exercise, engaging in emergency communications during a disaster or crisis, or simply exploring radio, having a reliable power source is paramount. Enter off-grid power solutions, offering freedom from traditional grid reliance and enabling seamless communication in remote locations. In this article, we'll delve into the intricacies of off-grid power, focusing on key considerations such as battery capacity, battery chemistries, solar panels, and solar charge controllers.
UNDERSTANDING BATTERY CAPACITIES
At the heart of any off-grid power setup lies the battery, storing energy for use when the sun sets or when power is needed off grid. Amp hour (Ah) ratings serve as a crucial metric in determining battery capacity—the higher the Ah rating, the more energy the battery can store. When selecting batteries for portable radio operations, it's essential to consider the power requirements of your equipment. Radios, computers, and other devices draw varying amounts of current, measured in amps (A) or milliamps (mA). By understanding the current draw of your equipment and estimating your power usage over time, you can calculate the required battery capacity to ensure uninterrupted operation.
As a very simple exercise and example, let's say your radio draws 1 amp on receive (meaning just sitting there powered on and listening to traffic) and you're carrying a 6 amp hour rated battery. If you do nothing but listen, you can do that for 6 hours before the power in the battery has been fully depleted. Of course this is in the perfect world of calculations and does not factor in considerations such as environment, battery health, etc. You can also expect your battery consumption to drastically increase when you start keying up the mic. So to ask how long will a radio system last on battery power, well that's often answered with "it depends".
Another consideration you definitely should not be overlooking is the specifications of the battery, specifically the maximum continuous and peak pulse discharge. You will need to compare these with the specifications of your radio and any peripheral equipment plugged into the battery and potentially adjust your transmit power accordingly.
For example, the Manpack 891 comes standard with a 6ah LiFePO4 battery (upgradable to 12ah) with a maximum continuous discharge of 12 amps. The integrated FT-891 transceiver can potentially draw up to 22 amps at full power and factoring in the Manpack's CPU circuit running at max could put the system close to 24 amp peak. Given this information, to be safe when using the 6ah battery, the transmit power setting should be limited to 50 watts. That's not to say you can't run the radio at full power in an emergency, but doing so you risk damaging the battery. Stepping up to the 12ah battery, requires no limitations however.
EXPLORING BATTERY CHEMISTRIES
When it comes to off-grid power, not all batteries are created equal. One of the most popular choices among portable radio operators is lithium iron phosphate (LiFePO4) batteries. Known for their high energy density, lightweight design, and long cycle life, LiFePO4 batteries offer a compelling solution for powering communication equipment in the field. Compared to traditional lead-acid batteries and others in the lithium family, LiFePO4 batteries boast superior performance, faster charging times, and reduced weight—a crucial factor for operators on the move.The brand of batteries I have found to be most promising and reliable is Bioenno Power. I use these batteries exclusively in my designs as they includes a Protection Circuit Module for internal cell balancing and protection against overcurrent, under-voltage, over-voltage, and short circuiting, ensuring your equipment remains safe and operational. What you'll find with LFP batteries is there voltage remains high until it doesn't. And what I mean by that is instead of a slow, steady parabolic decline in performance as you use the battery, you will see a sharp decline towards the end of their usage which maximizes adequate voltage to power your gear.
HARNESSING THE SUN: PACKABLE PANELS
Of course having the best battery made means absolutely nothing if you don't have a way to replenish the charge in the field or at least slow the discharge for extended use. In off-grid scenarios, where access to traditional power sources is limited, solar energy emerges as a sustainable and reliable alternative. Folding solar panels provide a compact and portable solution for capturing solar energy on the go. These lightweight panels feature photovoltaic cells that convert sunlight into electrical energy, which can then be used to charge batteries or power electronic devices directly. Efficiency is a key consideration when choosing folding solar panels, as higher efficiency panels can generate more power from limited sunlight, ensuring faster charging times and optimal performance.
I'm a huge fan of the affordable 100 Watt ALLPOWERS Solar Panels as they fold up fairly dense making them very packable albeit a bit on the heavy side at around 6lbs. For much lighter and slightly more efficient solutions most (including the military) turn towards SolarFilm which boast a much higher price tag along with their overall performance respectively.
SOLAR CHARGE CONTROLLERS: REGULATING THE FLOW
While solar panels offer a renewable source of energy, you shouldn't just go plugging in a panel to your battery all willy nilly! Proper management is essential to maximize efficiency and protect battery health. Solar charge controllers play a critical role in regulating the flow of power from solar panels to batteries, preventing overcharging and over-discharging. These intelligent devices monitor battery voltage and adjust charging parameters accordingly, ensuring optimal charging efficiency and prolonging battery life. With built-in features such as MPPT (Maximum Power Point Tracking) technology, solar charge controllers can extract maximum power from solar panels under varying environmental conditions, further enhancing system performance.
It's a good rule of thumb also to stick with proven charge controllers preferrably those made by or at least endorsed by communication equipment manufacturers considering not all charge controllers are created equal and some could produce very noisy emissions wreaking havoc on the RF spectrum. The top charge controller I recommend is made by Buddipole (known for their portable antenna systems) called the PowerMini 2 which is also loaded with features to monitor the charge and discharge rates throughout your operation.
Off-grid power solutions empower portable radio operators to stay connected and communicate effectively in remote environments. By leveraging lightweight batteries, understanding current draw, and harnessing the sun with efficient solar panels and charge controllers, operators can ensure reliable power for their communication equipment wherever their adventures take them. Whether it's for emergency preparedness or field operations, off-grid power is an essential capability that all operators should explore.