My “Power-Box” Project – Part #2

After starting, stopping, starting again, stopping once more…then putting the project on hold it was time to get back on this project. Does that sound confusing enough?

Well, when I started building this power box project I had this grandiose idea of having all these levels of redundancy and just a heck of a sophisticated power box. Yeah, remember what the KISS principle is? Well, somewhere along the way I went brain dead.

< Read Part #1 by clicking here >

Now, in my defense, the original power box that I had built worked! It had three batteries, a PWM solar charger built in, a relay to cut-over to a second bank of batteries should the big 100Ah AGM battery drop too low. There was an auto-switch from AC to DC if the AC failed. And there was more, much more. But, when I was all done with it, it simply was way, way too much…too sophisticated.

So I sat there in my shop one evening and was looking over the power box monstrosity thinking I had developed the perfect Frankenstein Monster. But, perfect in regards to theory only. In the field it would be too heavy, too many electronic parts, too complex, and just the wrong thing for the job. So, what did I do about it? I went back to basics. I reviewed the original “mission” and then went over the “Requirements & Restrictions.” Then it became clear to me to stop trying to overkill it.

Once I made up my mind to go back to the basic use I thought I should jump on it. Yeah, life had other plans for me, I was buried in other projects and it was just too cold out in my shop so I put the whole thing on hold till it got reasonably warmer. That was last week.

Once I started back on the project it went quickly and easily. I just wanted a power box that could –

  1. Provide reliable 12vDC to any of my radios.
  2. Provide reliable 12vDC to any combination of two of my radios.
  3. Provide a reliable means to charge at least 10 handheld radios at one time.
  4. Provide 12vDC power to other electronics as necessary.

I also wanted the following capabilities –

  1. Utilize 120vAC power if it was available but making sure there was auto-switch capability to DC power if the AC power was lost.
  2. Make use of a wide variety of solar charging capabilities; small 7w options all the to my dual-panel 60w solar charging system.
  3. Make use of a battery tender to keep the battery topped off.

Once I had that all clear in my head the “build” was pretty easy. Here is the list of components that I used –

Energizer 100Ah 12vDC AGM battery

Energizer AGM battery, Model: 31A 100 Amp Hour




MFJ 4230MV compact 25a power supply





Super PWRgate PG40S auto-switch

Ham In The Box - Super PWRgate PG40S by West Mountain Radio




For more operational capability I added –

Powerwerx voltage meter




A cigarette power outlet

Ham In The Box - Powerwerx Panel Mount Cigarette Lighter Socket Automotive Marine Grade




A dual 3A USB power outlet

Ham In The Box - Powerwerx Panel Mount Dual USB Socket 3 Amp Device Charger.




Various Anderson Powerpole chassis mounted connections




What I ended up with was exactly what I wanted. Sure, it was a little less operational time due to lower ampere hour availability, but it still met my basic mission just fine. And, it was a whole lot lighter and less complicated.

So here are the steps for the “build” –

Step #1 –

I started with an empty Rigid toolbox with wheels (model #) and added some Velcro to the bottom of the box. There is corresponding Velcro secured on the bottom of the battery. The battery weighs a whole lot! So it really isn’t going to somehow fall out of the box. The Velcro is used to keep it from moving around inside the box.

I wanted to ensure that I could get the battery in and out of the box without moving any other component and I wanted to keep the components spread out to reduce heat build-up as much as possible. It made sense to put the battery to the back of the box located as close to the wheels as possible for ease of movement. The power supply and auto-switch made the most sense to mount on opposite sides of the box.

Originally I wanted the power supply on the inside-front of the box but the mounting bracket pretty much dictated where that unit was to be mounted. With the location and positioning of each component figured out moved on to the the actual installs.

Step #2 –

The MFJ power supply doesn’t come with a mounting bracket, and it is a little off when it comes to standard dimensions for mounting brackets. I don’t like reinventing the wheel if I don’thave to. I took one of my spare Yeasu radio mounting brackets and added spacers to make it work for the MFJ power supply. I wanted the meter to be easily read but I also wanted to maximize the airflow around and through the unit itself. Hence, mounting it on the left side of the box with the bottom facing away from the side of the box.

Step #3 –

Next came the PWRgate and its proper placement. I already had the left side used and the front of the box I had decided to use for my Powerpole connections, meter, and power supply points. By default that left the right side of the box for the PWRgate. It was simple to find a decent spot and secure it to the side of the box.

Then wired up the “power out” to the Powerwerx chassis mount.

Step #4 –

I wanted to complete one side of the power circuit so I went ahead and placed the battery in the box, wired the battery to the PWRgate, and connected the PWRgate to the Powerwerx chassis mount. All wiring is high quality 10g wire to prevent voltage/amperage loss.

Notice that I have connected the power outlet to the PWRgate with a single 10g wire. Then off of that wire I used a connecter to splice in another 10g wire. Those are connected to the chassis connection point. Doing so gives me two sets of Anderson Powerpoles to connection equipment (i.e. radios) to. The 10g wire is more than enough to carry the carry the amperage.

Step #5 –

At this point I tried to implement some logic…power to the battery. So I installed another Powerpole chassis connection point on the left side of the front panel. This would be my connection to charging devices. Those devices could be solar chargers, a battery tender, or even another power box.

Notice that I ran the power in lines directly to the battery for the lowest amperage loss. But, I did place a fuse inline to protect the battery from any surge coming into the box.

Step #6 –

I wanted to be able to monitor the battery and get a feel for usage rate, remaining operational time, etc. So in comes the Powerwerx voltage meter. It was a simple install direct to on the front of the box. I located it in between a couple of horizontal structural pieces of the box. I used a 1-3/16” hole saw then used the standard plastic ring to secure the voltage meter to the box.

Step #7 –

As I mentioned earlier I wanted to add both a USB power outlet and a cigarette power outlet. The later provides a connection point for a wide variety of existing power options for various electronic and electrical equipment.

I prefer Powerwerx power outlets, one reason is the same diameter as the Powerwerx voltage meter. I placed a power outlet on either side of the voltage meter simply for atheistic. What I had to do was work it so the protective caps on the power outlets would open and not interfere with or be impeded by, the lip of plastic on the box itself.

Step #8 –

I had original thought to hook each of the power points and the voltage meter directly to the battery. Then I started to figure out having to fuse each line, etc. That is when I fell back to a Powerwerx distribution unit. Fuse one line going in, attached the two power outlets and the voltage meter and I would be good to go.

Step #9 –

I put the multi-meter to everything and it all checked out fine. Checked the voltage meter against the multi-meter and it checked out fine. Now it was time to test it out.

I was working on reviewing a dedicated 12vDC battery charging cradle for Baofeng UV-5RA so I figured why not test them both…and I did. I plugged the charger into the USB power point…fine. Then I plugged it into the cigarette power point…fine. I left it in there for four hours and it charged the radio battery up with no problems…no smoke, no smell of burning wires, and didn’t even burn up the charger base. All is good!

Next test was plugging in my battery tender that I am also reviewing, and it went right to work analyzing the big 100Ah Energizer battery, then went to charging it. I let it go overnight and came back in the morning to see it had topped off the battery and the tender was doing its thing to keep the AGM fully charged and ready.

A couple days later came the solar panel testing. Once again, everything performed exactly as designed. One note to make would be that whatever solar charging system must have its own charge controller since one is not built into the power box.

Finally came the AC power test. I plugged in the MFJ power cord, turn it on, and up comes the MFJ power supply just as it is supposed to. I dialed in the right DC voltage (13.4) to the PWRgate and all was good…no blown fuses and power coming out just as designed.

Then came the “switch” test. I put a load on the power box made sure the AC was working just fine and that the battery was standing by. Then I turned off the AC power. The PWRgate auto-switched from the AC power over to the DC power from the battery without any interruption of power. I did notice the power dropped from 13.4v to 13.2v. But that is to be expected when running off of the battery.

Everything worked exactly as I had planned and hoped it would.

Next test will be draining the batteries from 10 Baofeng UV-5RA radios. Then I will use a variety of DC charge adapters hooked into the Baofeng charging bases to see how long it takes to charge up all 10 batteries and the draw-down on the 100Ah AGM battery.

Then I will draw-down the 100Ah AGM battery and hook up the AC power to see how long it takes the PWRgate to bring the AGM battery back online and back to full power. But in the meantime, I leave the MFJ power supply on and it will keep the 100Ah AGM battery fully charged and ready to go.

Stay tuned for more testing results and another idea or two!!!

2009 - 2020 Copyright © ~ All rights reserved
No reproduction or other use of this content 
without expressed written permission from
See Content Use Policy for more information.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s