Home Projects Ammo Can Battery Box
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PostHeaderIcon Ammo Can Battery Box

Written by Jasper Raven KD0CSE

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After deciding what to do for Field Day 2010, a spare ammo can looked like the ideal portable power source for small electronics.  Two sealed 7.5Ah lead-acid batteries fit side by side in a 5.56mm ammo can.  Two batteries were chosen instead of a single larger one because I preferred a certain trade-off.  I'd rather have it be clearly known I have hit my half-way point of total usage instead of simply having one large battery.

Photos, the bill of materials, and a panel mount drawing are all provided for reference.  Two terminal blocks and a fuse holder were glued to the inside of the lid using some "Liquid Nails" adhesive.  Just enough glue was put down that when I pushed the parts onto the glue they had a full contact area.  I smeared them around a bit using the part to roll out any bubbles and start to set the glue.

The terminal blocks and fuse holder could be more simplified, but my reasoning was to have 1-wire connections to screw terminals, with each line having a fuse.  Also I had considered using reset-able circuit-breaker style ATO fuses but preferred keeping it simple and used plain 10 Amp ATO fuses.

All panel mount components were put on the embossed label (hinge-side) of the can.  The lid opens with wires to batteries on the end farthest from the hinge, keeping them loose and accessible if the lid is detatched from its bullet hinges.  The final wiring was wrapped in 1/4" split loom to keep things neat.

Drilled holes for components on the front face are spaced roughly from outside surfaces with some easy fractional inch distances.  The toggle covers were put in place so that the power is normally off, and the 1st battery is normally connected.  The red toggle covers keep it from being accidentally turned on.  The right switch activates the binding posts (and 12V socket, and power LED).  The left switch toggles between the first and second battery as the source.  The binding posts are used as a common point for the power leads, the LED leads, and the 12V socket leads.  The pictures show a red power LED, but I changed my mind later and swapped in a green assembly.

The batteries were held down only by gravity, and kept in place using cardboard shims against the outer walls.  The shims kept them in place, but obviously won't work if the container tumbles upside down.  I have since added double-sided velcro tape to hold them in place vertically.  The velcro tape was fastened to the can using more liquid nails glue.  This hold them securely in place and still makes it easy to swap out the batteries when needed.  Because they are located against the back end of the box, the container is not balanced on-center.  The box only feels about 1 or 2 inches off-center so it remains level and comfortable to carry.


                                                       Battery Box Bill Of Materials

Item # Qty
Description Vendor Part No. Unit Cost Net Cost
1 1
M2A1 Ammo Can Army Surplus Sales N/A $3.0000 $3.00
2 2
7.5 Ah VRLA Battery Interstate Batteries SLA1075 $40.9900 $81.98
3 1
4-gang ATC fuse block Del City 73810 $4.8200 $4.82
4 2
4-gang screw terminal block Del City 70014 $1.6600 $3.32
5 1
dual binding post Radio Shack 274-0718 $4.9900 $4.99
6 2
DPDT o-ring screw term on-on Del City 7300127 $1.1500 $2.30
7 2
toggle switch cover Del City 73200 $4.8400 $9.68
8 1
green LED assembly Radio Shack 276-271 $1.9900 $1.99
9 12
Standard .25, Fem, QD HS Del City 952085 $0.2700 $3.24
10 30
Ring Terminal, 8 stud, HS Del City 964205 $0.4200 $12.60
11 4
10A ATC fuses Del City 78105 $0.1400 $0.56
12 1
12V socket (Marinco 12VRC) Del City 73542 $7.8700 $7.87
13 4
1/4” spiral cut loom, UOM=FT Del City 722 $0.1037 $0.41
14 4
Red primary wire, 14ga, UOM=FT Del City 1114101 $0.1234 $0.49
15 4
Black primary wire, 14ga, UOM=FT Del City 1114105 $0.1234 $0.49