Hi. Simple Circuit here with another simple project. In fact, it’s so simple I’m not sure it qualifies as an Instructable – more like a mini- instructable, or maybe a micro-instructable. Recently I needed two CR2302 button batteries, but they’re like $4.50 a pair at most big box stores. So I did what any good DIYer would do and shopped for them on the internet. I found 100 for around $12.50 – what a deal! Well, for those of you who are familiar with the expression, “Penny wise, Pound foolish”, that applies in this case. Yes, I got my two batteries for 12.5 cents each, but I was also stuck with 98 other batteries that I probably will not use in my lifetime and that cost me $12. So, the question of how to use all those batteries resulted in this project.
Step 1: Initial Thoughts
The batteries came in plastic trays containing 20 or 40 batteries each. The first idea was to store them in such a way as to extend their shelf life as much as possible. I got out the kitchen Food Saver and vacuum packed each of two trays (photo above). I have no idea if this will prolong the battery shelf life or not, and this really has nothing to do with this Instructable, but I just think it’s cool to vacuum pack stuff. Anyway, back to the project.
Step 2: Getting Started
The most practical idea was to use multiple batteries in series for various projects requiring different voltages. By stacking the batteries you can produce any voltage source that’s a multiple of 3 – 3, 6, 9, 12, 30, 300 volts. I rarely have a project that requires more than 12 volts, so in terms of practicality (and possibly safety) I set the upper limit of my battery holders at 12 volts.
Things needed for this project:
Nickel size plastic coin tubes with screw-on caps
7/8” diameter wooden dowel
Springs, lots of springs
A few roofing nails
Stranded hookup wire
Tools and skills needed for this project:
A drill press is HIGHLY RECOMMENDED. Alignment of holes drilled in wooden spacers must be fairly precise, and this is more difficult to do with a regular corded or cordless drill.
Basic soldering skills.
The idea was to make a battery holder in the shape of a tube that could hold one to four button cell batteries, depending on the voltage desired. A screw-cap coin tube that holds $2 worth of nickels is used as the battery holder, since CR2032 cells fit snugly in the tube. A wooden spacer containing a spring is then added to hold the battery leads firmly against the batteries. The spacer is made from a 7/8” diameter dowel, which also fits snugly into the coin tube.
NOTE: The sides of the coin tubes I purchased were not completely parallel from top to bottom, so I had to do some sanding of the spacers to get them to slide easily up and down the tubes.
Step 3: Spacers
An assortment of springs can be obtained from any hardware store. After experimenting with various configurations of springs and spacer lengths I found the following two to be most useful:
A) 2’’ to 2-¼” spacer housing a 1-5/8’’ x 11/32” compression spring
B) ¾” spacer housing a 51/64” (about ¾”) x 3/8” compression spring
Spacer A: Cut the spacer to size making sure the cut is perpendicular to the long axis of the dowel (I used a miter saw for all cuts). Drill a 5/16” hole ¾” deep in the center of one end of the spacer. The spring will be seated in this hole. Then drill a 5/32” hole through the center of the other end of the spacer to connect to the first hole. A battery lead (usually anode lead) will be threaded through this hole, and wire up to 18 gauge will easily fit through it. This spacer with drilled holes is shown in the photo above..
Spacer B: Cut the spacer to size (3/4” long) and drill a 3/8” hole ¼” deep in the center of one end. Drill a 5/32” hole through the center of the other end of to connect to the first hole.
NOTE: None of these measurements are carved in stone, and you may find that other spacer lengths and spring sizes are more appropriate for your own needs.
Step 4: Battery Leads
I initially tried soldering leads directly to the springs and to contacts salvaged from old flashlights, but found this to be neither easy nor very practical, so I decided to make leads as separate components that could be used interchangeably in various configurations. Galvanized roofing nails proved to be perfect contacts for the leads. Remove the zinc layer from the nail head with sandpaper or a wire brush, cut the shank of the nail to ½” to ¾” in length, and solder on the wire lead. I used 18 AWG stranded wire because I have lots of it and it’s about the same diameter as the nail, but smaller wire will probably work just as well. Some of the leads are shown in the top photo above.
I covered the solder joints with heat shrink tubing and coated the undersides of the nail heads with silicone to electrically isolate the leads from the springs, just in case the springs might produce some unwanted inductance if electrically charged. Probably paranoia on my part, but you never know.
Finally, drill 5/32” holes in the center of the bottom of the coin tube and the screw-cap, and you’re good to go. Final assembly is shown in the bottom photo. Notice the spring tapers slightly. The smaller end is inserted into the spacer.
Step 5: Demo
Need a 3 volt supply? Pop in one button cell (top photo). Need 12 volts? Pop in 3 more cells (bottom photo).
Step 6: More Batteries
I should probably stop here, but no. These battery holders can be used for other batteries with a little modification. The configuration for one AA battery is shown in the top photo. Spacer B is used here along with a bushing to hold the battery made from ½" PVC conduit one inch in length. I don’t know who would ever need a 1.5 volt source, but if so, this is it. A more practical battery arrangement using a 12 volt A23 battery is shown in the bottom photo. This holder uses spacer B at the top and an additional spacer about 1-5/8’ in length with a 7/16” hole drilled ¾” deep in one end to hold the battery.
NOTE: Occasionally when first assembling a battery configuration, the leads will not seat properly and no current will flow. If this happens, undo and reattach the screw-top or gently rap the tube holder against a flat surface. This will seat the leads properly.
Step 7: DIY Batteries
No battery? No problem. Just make your own using one of the coin tubes. The top picture shows a little battery I cobbled together in 5 minutes using a 12 penny galvanized nail, a piece of 8 AWG copper ground wire, and a little vinegar. A coin tube battery holder also serves as a great case for the penny battery from the Instructable, “How to Turn Spare Pocket Change into DIY Batteries” by The King of Random. The penny battery in the lower picture produces about 6 volts.
That really is all for now. I hope you found this Instructable of some use, and as always, comments are greatly appreciated.