Ammo Can 12V Power Supply - Updated!




About: Be limited only by your imagination.

This is a simple power supply.  I had some 12V batteries from an old alarm system and telephone backup system.  I simply wired them in parallel and wired in a power outlet and alligator clips.  I currently use the alligator clips to attach the batteries to a trickle charger.  When not charging I put two ziplock minibags on the end to prevent their shorting out.  The power outlet is simply drilled into the top of the ammo can.

You can see a picture of the unit powering a lamp that I retrofitted with a 12V LED car headlight.  I've testing the duration of this and stopped after 36 hours.  I would estimate it would last at least twice as long. 

I also use this to power my bicycle compressor.

I'm not sure if it has the amps to jumpstart a car.  Combined the batteries put out 7.5 amp hours.

I plan to get a power plug so that I can charge the unit with the lid closed but I will keep the alligator clips because you never know when you need to directly wire something.  I will also probably get a rubber stopper to put into the top of the outlet when not in use to keep out dust or moisture.

The total cost of making this was $0.  I had all the materials lying around.  The materials included:
-ammo can
-12V outlet
-two old 12V batteries
-two alligator clips
-trickle charger
-two wire nuts
-electrical tape

18 SEP 2013
- I modified the battery input system.  (Thanks Klee27x) Rather than add posts to the box itself I built a charging station so that I can keep the profile of the ammo can intact.  Also, I worried a bit about shorting the posts if it was integrated into the box itself.  The charger is made completely of reused components including a piece of 3/4 inch wood that is cut into a T-shape so that the alligator clips from the charger can't short.  It has two bolts with nuts fastening them.  There are two washers underneath and one on top.  Wire is wound between the two lower washers and the nut is tightened to keep it all in place.  I've identified which side is red and which is black. 

28 SEP 2013
- I realized I can use the battery input system as an output system too.  In the last picture you will see that I am powering a Jeep VIC from the posts.  I hope to put the VIC into a clock as per

28 SEP 2013 - I found this cap in my junk box.  It was from an old automobile lighter outlet.  This will keep out dust and moisture in the field.  See the picture

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16 Discussions


2 years ago

forgot to mention, to isolate any vibration or bouncing around I use canned sprayfoam (for window cracks)

I made a copy of the battery with wood and a spacer for the wirering, covered in skidwrap, spayed the inside of the box and voila!! nothing moves and no cutting in soft foam required! plus everything is a perfect fit!!

1 reply

2 years ago

I did this setup with 3 rocker switch with led and a 12-volt 12ah SLA battery,

my latest test came out with 10 hours running time on my boat

1-Lowrance fish finder

1-led rear navigation post

1-bow light (12V bulb)

1-36" marine led strip

Glued the box with ZIP cocking for easy removal for winter and outfeeded wires for charging via a 12v outlet.

now I'm being ask to make them to most of my friends !!

will be making a new one with a panel with carling narva rocker switch. i'll try to post photo when done!!!


3 years ago

I thought about doing something similar but having the DC outlet on the inside of the box with some kind of thin sheet metal installed inside. That way it would be somewhat waterproof. Also, using foaming insulation to hold the batteries in place securely. You would have to chip out the insulation to change the batteries but they wouldn't be bouncing around. Great idea for going camping and if you hooked two 12 volt batteries in parallel it should last longer and install a A/C charging port to charge the batteries

1 reply

Reply 3 years ago

Great ideas. I have not had any problem with batteries rattling. They fit rather snugly, but that is just a happy coincidence. If you used foam insulation it would be great. You never have to take the batteries out because they recharge and so it's an almost permanent solution.


5 years ago on Introduction

Quiet clever, could be updated with some Lithium motorcycle batteries. Expensive but very light.


6 years ago on Introduction

Alligator clips covered by plastic bags, huh? I would sooo redo that part. I'm thinking screw post terminals/nuts on top with a barrier between the posts to prevent them from being shorted.

3 replies

Reply 6 years ago on Introduction

Uh oh. This is a slippery slope you're heading down. It starts with one. Next thing you know you have custom connectors for other stuff. And one day, you'll make a custom connector to connect another custom connector to something else. And then one day you will go crazy looking for a custom connector. :) Good work, but heed my crystal ball. :)


6 years ago on Introduction

Unfortunately not much and not for long. Altogether the batteries have 7.5 Ah of power. My guess is that you could run lights for a couple hours or a drill or fan for a couple of minutes.

The box is really useful as an emergency supply for lighting. I can hook up both the lamp I showed and a long string of red LED's. (Red preserves night vision). I've also used it for the bicycle air compressor in my workshop. The compressor usually plugs into the car's supply but it's inconvenient to have to position the compressor near the car. It's also done really well when I needed to power my iPhone during blackouts.


6 years ago

Great stuff. Can you use a converter and go to AC. What kind of run time would you have if you kept it at 100w?