Hello Operators.
I've been watching this thread for some time and thought I would share my own Journey and evolution with portable power for amateur radio communications. Not too long ago I was using in nickel metal hydride batteries, as the primary power source for my radio communications. Although I enjoyed using the Enelope nickel metal hydride batteries, their energy density is nothing compared to lithium ion or lithium iron phosphate. The price was right however.
But after walking 40 kilometers on an off-grid emergency deployment exercise, I realize I needed to increase the storage capacity of whatever energy storage solution I decided to carry with me. That left me with two options.
- a larger or parallel nickel metal hydride pack with increased weight
- finding a battery chemistry with increased energy density for the same weight
I did go on to use the nickel metal hydride packs with it pwm charge controller for quite some time. Now I've repurpose that charge controller, as a standby power go box with a 9 amp slab, wall mounted inside a small Pelican case.
The first upgradeThat's when I built the QRP battery pack
http://oh8stn.org/blog/2017/06/08/diy-34s-li-ion-qrp-battery-pack/ . This first pack was a lithium ion battery pack with 3.4Ah capacity. I used four 18650 batteries in series and a battery balance and protection board, to manage low voltage, overcharge, Short Circuit, and balance the cells.
I could connect the qrp battery pack to any of my solar panels, using the combination of battery pack and solar panel for sustained Communications in the field. Although the complexity of the build might seem daunting to many operators, the result is a stable lithium ion energy storage solution, with simultaneous charge and discharge capabilities. Fortunately I needed to use a DC/DC CC/CV power supply with the qrp battery pack. That was okay until later on when I found a better solution.
The second upgradeThe qrp battery pack was the first step in ultra-portable off-grid power for amateur radio. Unfortunately that pack could be looked at as nothing more than a rapid deployment, high speed low drag storage solution. Up until that point my solar panels we're still critically underpowered or overweight. I had the 10 watt solar briefcase from Harbor Freight. This was a total waste of money. Then I settled on two Goal Zero Nomad 7. The Goal Zero panels held me over for a while. They were not too heavy, they had both 12 volt and USB output and they could be chained together easily. Unfortunately their pieces of crap and the designer should be burned alive at the stake. The point of failure on The Nomad series of solar panels is the little box which holds all of the electronics. The cable breakout box works itself loose causing a short circuit in the worst-case or no connection at all. And despite their best marketing these is neither waterproof or water-resistant in any way. This led me to the PowerFilm F15-1200 20w
http://oh8stn.org/blog/2017/06/16/portable-off-grid-power-for-amateur-radio-part-1/ flexible thin-film solar panel. By itself it weighs less than one of the Nomads, but brings in 1.2A of energy collection with a big reduction in weight. It can also be damaged without becoming completely useless. The only downside is the price.
Upgrade number threeWith the acquisition of a good panel I also needed to invest in a good solar charge controller. I'm pretty sure most of you will find this acquisition excessive, but it's my opinion that we spend too much money on trying to hack a solution together instead of buying the right thing the first time just once. That brought me to the Genasun GV-5 solar charge controller for lithium iron phosphate batteries
http://oh8stn.org/blog/2017/06/20/man-portable-off-grid-power-for-amateur-radio-part-2/ The Genasun is a 5 amp solar charge controller which is completely RF noise free! One can directly connect a lithium iron phosphate battery pack (with bms board), a solar panel, and a qrp radio on the load port. The BMS board in my qrp battery pack was compatible with both lithium ion and lithium iron phosphate depending on the input voltage. So to use my little qrp battery pack I simply had to swap out the lithium ion batteries for lithium iron phosphate 18650 cells. That was the Prototype!
Digital Field Day 2017Last weekend (June 34 2017) at field day I used this combination of energy storage, solar collection, and Battery management to power my digital Field Station for 4 hours. I was using a digital mode called FSQ, to interact with two operators. The first operator was in the south of Norway, while the second operator was in Netherlands. Most of you already know I meant 65° North in Finland. We did text chat, exchanged images, interacted with the automated functions of FSQ, ... as a test for establishing reliable low-power digital Communications from the field. The test also confirmed that the combination of gear provided a lightweight Ultra portable off-grid power solution for field communications.
Here are a few things I learned.
- Hacking cheap chinese gear and learning by doing so are fun, but at some point we need to start engineering reliable solutions for off-grid comms
- the investment in quality gear will often solve more problems then immediately apparent. For example the two Goal Zero panels were cheaper than the Powerfilm, but the PowerFilm saved me weight, increased solar collection, and reduced the complexity of my system
- integrating the solar charge controller and lithium iron phosphate battery pack gave me simultaneous charge and discharge capabilities. That means no more fumbling around with AA batteries, swapping out battery packs, ...
The next stepSo now that I know that everything works as one integrated system, it's time to increase the storage capacity of my system. The 3.4Ah pack does a great job in the summer months at 65 degrees north, because we have 24 hours of sunlight. For winter operations in the field I'm going to double up on the solar panels (adding a second PowerFilm F15-1200), and in the coming weeks start building a 10Ah version lithium iron phosphate protected battery pack. This offsets the fact that we have almost no daylight during the winter months.
Finally a word of caution. I once review day cheap Chinese solar panel on my channel. It was called Choetech 19w folding panel. I finally realized the gimmick with these cheap Chinese panels. They all have a USB output, and they probably are accurate in regards to the potential wattage they can collect. However they deceive us when saying the USB output has two amp rating or 2.5 amp rating, because the solar panel itself could never generate that amount of amperage, without having several of those panels in parallel. They're not lying they're just not telling the whole truth. If you're into preparedness Communications, it's time to start building or buying your own quality gear.
de oh8stn