My Field Box Survival/Power Project

[dharbert]

I'm somewhat of a tinkerer, and my latest project is a survival/hunting/emgergency field battery box. This is a relatively easy and inexpensive project to make, depending on how fancy you want to get with it and they types of gear contained within.

Parts List:

Plano Field Box
12v 7ah Battery
12v Power Outlet
14 guage to 16 gauge wire
14 gauge to 16 gauge female slide connects
25mm Hole Saw w/Drill Bit
Wire Stripper/Crimper
1" Thick Soft Crafting Foam
1" Thick Hard Foam Block

Place the battery with the terminals right side up and facing the rear of the box (hinge). Unscrew the outer shell of the 12 volt power outlet and use it as a template to mark a hole on the outside of the box. Use a black marker to mark a spot on the hinge side of the box next to the battery. This will be where you will drill the hole for the 12 volt power outlet. Place the drill bit in the center of the cirlce that you marked earlier and drill a hole through the box. Now, place the 12 volt power outlet through the front of the hole and screw the outer shell back on it from the inside. Cut an appropriate lenth of wire for the positive and negative terminals and attach a female slide connect at both ends. Connect the 12 volt power outlet to the battery. At this point you can plug in a 12 volt accesssory into the outlet and ensure that everything is working correctly.

Next, cut a 1" x 3 1/2" piece out of the hard foam block and wedge it in between the battery and the side of the box, just behind the power outlet. This serves two purposes. It will help keep the battery in place and it will prevent gear stored in the bottom of the field box from making contact with the power outlet. Now, cut a 9 1/2" x 4 1/4" piece out of the soft crafting foam and place it on top of the battery. This also serves two purposes. It separates gear stored in the top of the field box from gear stored in the bottom of the field box, and also prevents gear stored in the top of the field box from making contact with the battery terminals.

Even though most of the field box is taken up by the battery, there is still plenty of room for other gear. Depending on what you want to use this box for (hunting/fishing/camping/emergency/vehicle), you can fit several other items it. In the box that I made in the picture, in addition to the battery I have 100 feet of 550 paracord, 2 carbineers, an LED flashlight, eating utensils, matches in a waterproof case, 12 volt USB adapter, knife, multi-tool and a flare. The weight of the box with this loadout is between 5 and 6 pounds.

The battery that I used for this project is 12 volt 7 amp hour, providing a total of 84 watts. This will charge an iPhone from completely dead to full charge in about 1 hour and 15 minutes. The number of charges you can get before discharging the battery depends on the device and the current charge of the device. It is not recommended to discharge the battery past 12.2 volts (50%). This can be tested in the rest state of the battery (no load) by using a multimeter. For those who are curious, an iPhone 4 battery holds 5.18 watts and a iPod Touch battery holds 2.96 watts.

Overall, this a fun, easy project that has several uses. Your mileage may vary, of course, depending on the materials used and the purpose that you have envisioned for the field box. Right now I'm working on another variant that will be used purely for a power supply, with 2 x 12v 7ah batteries, 2 x 12v power outlets, 100w inverter and an input for solar power to recharge the batteries.

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[dharbert]

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[dharbert]

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[Synchronizor]

Pretty neat little setup. Back when I was involved in some NASA-sponsored testing using high-altitude balloons, we had a couple similar 12V battery units for powering radios and other equipment in the field during launches and tracking.

One thing I would suggest would be to find a cheap automotive voltmeter, install it in the side of the box, and wire it to the battery with a momentary-on button or switch. That'll let you can check the charge as often as you like without having to take out everything above the battery to access it with a separate multimeter each time. This could be especially handy for experimenting with solar charging.

[dharbert]

One thing I would suggest would be to find a cheap automotive voltmeter, install it in the side of the box, and wire it to the battery with a momentary-on button or switch. That'll let you can check the charge as often as you like without having to take out everything above the battery to access it with a separate multimeter each time. This could be especially handy for experimenting with solar charging.

The voltmeter is a good idea, but only serves a single purpose. I opted to install a couple of battery jumper studs underneath the 12v power port on the outside of the box. This will allow me to not only check the voltage of the battery using a multimeter without having to open the box, I can also use the jumper studs to recharge the battery via a wall charger or solar panel, and also to supply 12 volt power to various devices using alligator clips instead of the 12v power port.

I've also found a better way of packing items into the box so it can hold more. In addition to the 12 volt battery and power port, it now contains a 140 watt power inverter, USB charger with 3' cable, LED flashlight, 3 x AAA replacment batteries for the flashlight, multi-tool, knife, waterproof matches in a tube, 15 minute flare, 100' of 550 cord, 5 carabineers, emergency blanket, stainless steel wire saw, eating utensils, compass/thermometer/whistle combo, and there is still room for a couple of other small items. You can fit quite a lot of gear into these small ammo/field boxes.

I did some testing with this while on a job, and it was able to run my laptop for 30 minutes, which pulled the battery down to 50% charge (~12.2v). It should be able to charge a completely dead iPhone at least 8 times and only pull the battery down to 50%, and charge a completely dead iPod touch 14 to 16 times and only pull the battery down to 50%.

I've never messed around with solar power before, so I purchased a small 2 watt solar panel to test out with this field box. It is a 12 volt solar panel, but it puts out a surprising amount of power in full sunlight. The open circuit voltage of this panel is 23 volts! It has an internal charge controller and reverse current protection to keep 12 volt batteries from overcharging, and also keep the batteries from discharging into the solar panel.

This battery should last a while if I only discharge it 50%, and even longer if I only discharge it 20%.

[Synchronizor]

The voltmeter is a good idea, but only serves a single purpose. I opted to install a couple of battery jumper studs underneath the 12v power port on the outside of the box. This will allow me to not only check the voltage of the battery using a multimeter without having to open the box, I can also use the jumper studs to recharge the battery via a wall charger or solar panel, and also to supply 12 volt power to various devices using alligator clips instead of the 12v power port.

That still requires you to bring along a multimeter, though. There are some nice, compact voltmeters that install right in the side of the box and would let you keep an eye on the battery more easily. I guess it would depend on where and how often you need to check the voltage.

[dharbert]

There are some nice, compact voltmeters that install right in the side of the box and would let you keep an eye on the battery more easily. I guess it would depend on where and how often you need to check the voltage.

Yeah, I might end up installing a digital voltmeter as well.

As I said in my original post, the contents of the field box depend on what you intend to use it for and the environment you plan (or didn't plan) to be in. I've changed the configuration of mine a few times. I'm still amazed at how much you can fit into these field boxes, especially with a 12v battery and power port already taking up half the box.

I use two configurations. In one configuration I can have all of the items shown in the following pictures, with the exception of the power inverter. In the other configuration, I can have all of the items shown with the exception of the bivvy and the medical kit. So basically the only difference between the two is I can either have the inverter in the box, or the bivvy and medical kit, but not both at the same time. I use a separate 2w solar panel to recharge the 12v battery.

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[dharbert]

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