Ham Radio EMCOMM Go Kit – Power Box v2

I only built the previous version of this box a few months ago, but I learned a lot from building that case. The main thing I learned is that rack cases aren’t necessarily the best option for a power case. Rack cases are great for radios because they provide ready access to the front and rear of radios and other gear. For a power box the extra lids, bulk, and weight of a rack case don’t provide enough benefit to overcome the drawbacks. I also quickly realized that I really don’t need an inverter. I found a very compact and high performing 12V adapter for my laptop that makes the inverter unnecessary. This all combined with the awkward power wiring and inadequate power monitoring of my previous case pushed me to rethink my power box.

Case

I wanted a case that would make the most of the small size of my 40 Ah lithium-iron-phosphate battery. The one I ended up using is only $15 at Lowes. The battery sits in the case and is kept from shifting by stacks of cardboard cut and glued to fit the taper of the case. This works well to keep the battery stable while allowing for easy removal when needed. The power circuit is wired with 10 AWG wire and the battery is fused using 40 Amp ATC fuses.

Power System

From the battery the power flows through a West Mountain Radio PWRcheck. This device is an inline power monitor that measures voltage, amperage, power, and amp hours. It can also log power usage and provide a battery gauge when the battery’s amp hour rating is input via the unit’s control software and USB connection. The PWRcheck can also be setup to alarm at low and high voltage along with other features. The PWRcheck then feeds a WMR Epic PWRgate. I used this device in the previous build and it works well as a battery charger in addition to channeling power from solar, battery, or power supply inputs to the output. Both the PWRcheck and PWRgate are mounted using heavy duty velcro, the PWRcheck to the top of the battery and the PWRgate to the side of the case. This allows for easy removal, while also securely holding them in place. The PWRgate’s solar and power supply inputs and its power output are wired to powerpoles mounted to the outside of the box. All wiring was done using 10 AWG wire except the solar which is 12 AWG since it doesn’t carry as much current. I also used blue & gray powerpoles for the solar connections to differentiate them from the others for easy identification. The final piece of the power system is a WMR RIGrunner 4005 mounted to the outside of the case using heavy duty velcro. This allows flexibility to either provide power distribution from the case itself or move the RIGrunner to another location and provide power from there via an extension cable from the power box. All of the power system devices are rated for 40 Amps of continuous current which is more than enough for my purposes.

Operation

I really wanted to keep this build super simple and flexible while maintaining a lot of functionality and I feel good about how it turned out. The case itself is just the battery, power monitoring and a charging/distribution system. Everything is modular, light and there aren’t any unnecessary devices or wiring. This new version of the power box weighs in at only 16.5 lbs, a little over half the weight of the previous build. My previous go kit total weight was about 70 lbs (radios + power) and the new arrangement totals about 69 lbs. This doesn’t seem like much of an improvement, however, since I rarely need both radio cases I end up saving quite a bit of weight for real world applications. For example, a Field Day or QSO party deployment (HF + power) with my new cases totals about 46 lbs, over 20 lbs lighter than my previous iteration and over 50 lbs lighter than if I used my lead acid battery. I especially like how much less bulky this version of the power box is and the ease of portability that this provides.

Update (June 2018)

After using my new power box for a little while it became apparent that it would be a good idea to have a more convenient way to turn off the power, and therefore minimize any discharge from the battery, than simply unplugging the main powerpole connection. To this end I decided to remove the fuses and in their place put a 40 A circuit breaker. This breaker is bolted to the outside of the case, making it very convenient to access compared to the fuses. This change also necessitated rerouting some of the wiring, but I think it ended up better arranged than before. I used the power box in this configuration for Field Day with my solar panel and everything worked perfectly.

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