Heat Shrink Coin & Button Battery Holder

To power a DIY LED lab project for a group of inexperienced students, I was looking for an inexpensive, clean, and visually attractive solution to attach a Coin / Button battery to a LED circuit.

After trial and error, I found the following method of heat shrinking wire leads onto the Coin / Button battery terminals to be relatively easy and low cost along with conserving space, providing battery short protection, and was visually attractive.

For lack of a better name, I refer to it as a “Heat Shrink Coin & Button Battery Holder”.

Summary of Procedures:

1. Getting your Materials (Parts & Tools)
   • Get Parts: Coin / Button battery (size dependent on your project), 22 Gauge Solid Wire, Heat Shrink Tubing (diameter size dependent on your battery)
   • Get Tools: Diagonal Cutters, Wire Strippers or Utility Knife, Needle Nose Pillars, Scissors or Utility Knife, & Heat Gun or Lighter
2. Preparing the Wire Leads
   • Cut 2 (qty) Wire Leads (22 Gauge) to desired length for your project
   • Strip ends to roughly the length of the Coin / Button battery diameter
   • Bend the exposed wire ends into a spiraling shape
3. Preparing the Heat Shrink Sleeve
   • Select Heat Shrink Tubing diameter that securely holds battery
   • Cut piece of Heat Shrink Tubing roughly 1.5 times the length of the battery diameter to make a sleeve
4. Inserting the Coin / Button battery into Heat Shrink Sleeve
   • Stretch internal diameter of Heat Shrink Sleeve if needed
   • Place Coin / Button battery into Heat Shrink Sleeve
5. Inserting Wire Leads into Heat Shrink Sleeve
   • Insert Wire Leads between battery and Heat Shrink Sleeve
6. Applying heat to Shrink Sleeve
   • Apply heat to shrink the Heat Shrink Sleeve securing the Wire Leads to the Coin / Button battery

I did attempt other approaches to secure a Coin / Button battery to a LED circuit; however, my results were mixed.

• Incorporation of a button battery holder: Due to confined space and the significant cost adder per project kit, I decided that a molded battery holder was not a viable option.
• Variety of taping methods (including some illustrated here on instructables):  Taping was not giving me the clean look I desired.  Nor was the taping method necessarily easy when attempting to position and secure two loose wire leads to the Coin / Button battery terminals as you wrapped tape around it by yourself.
• Solder directly onto the battery terminals:  Soldering to the battery yielded limited success and I was concerned with my student’s ability to utilize this method along with any potential battery damage due to excessive heat.  I did evaluate batteries with soldering tabs; however, I found them to be a significant cost adder compared to a regular bulk Coin / Button battery.
• Conductive glue / epoxy:  Yielded similar frustrations as taping and came with the additional concerns around the chemical makeup.

Parts

• Item: Coin / Button Battery
  • Use: Intended to power your electronic project.  I have used a variety of Coin / Button batteries including CR2032 (3v 20mm × 3.2mm), CR927 (3v 9.5mm × 2.7mm), CR1025 (3v 10mm × 2.5mm), LR44 (1.5v 11.6mm × 5.4mm) with this process.  The type of Coin / Button battery really depends on what your power needs are.
  • Price: Depends on supplier and volume.  If you are buying in large volumes, I recommend hunting around for the best deal.
• Item: 22-Gauge Solid Hookup Wire
  • Use: Used to make battery leads which provide continuity from battery to the desired circuit.  I prefer using two colors (Red and Black) to label polarity when attached to the battery; however, use whatever color you want.
  • Price: 22-Gauge Solid Hookup Wire is pretty inexpensive.  On average it costs less than 1 cent per inch.  At your typically electronic store, you can pick a 25’ spool for about $3.00.
• Item: Polyolefin Heat Shrinkable Tubing
  • Use: Provides a compression / mechanical bond of the two individual 22 Gauge Wire Leads to the Coin / Button battery terminal once shrunk when heat is applied.  Each Coin / Button battery usually requires a different Heat Shrinkable Tubing diameter size.
    In my trials, I have found that the following batteries work well with the following 1-2 Heat Shrink Tubing diameters and sleeve lengths:
    • CR2032 (3v 20mm × 3.2mm) – Heat Shrink Diameter: 1/2 inch; Sleeve Length: 1 1/4 inches
    • CR927 (3v 9.5mm × 2.7mm) – Heat Shrink Diameter: 1/4 inch; Sleeve Length: Length  5/8 inch
    • CR1025 (3v 10mm × 2.5mm) – Heat Shrink Diameter: 1/4 inch; Sleeve Length: Length 5/8 inch
    • LR44 (1.5v 11.6mm × 5.4mm) – Heat Shrink Diameter 3/8 inch; Sleeve Length:  Length 5/8 inch
  • Price: Price really depends on volume and from where you purchase.  For example, allelectronics.com has 1/2" X 4' Heat Shrink Tube in black for about $2.50.  So if you were using that tubing for the CR2032 batteries, which needs a length of about 1 1/4 inches for the sleeve, you would get about 38 sleeves out of those 4 feet at an average cost of 6 cents a sleeve.
• Item: Small Zip Tie / Cable Tie (Optional)
  • Use: Apply additional compression to the heat shrink sleeve, wire leads, and Coin / Button battery package.
  • Price: Price really depends on volume and from where you purchase; however, it is typically an average cost of less than 1 cent a tie.

Tools

• Diagonal Cutters: Cutting the 22 Gauge Hookup Wire
• Wire Strippers or Utility Knife: Removing insulation from wires
• Needle Nose Pillars: Makeshift jigs to wrap the bare wire ends around and something to finesse the battery into the Heat Shrink Sleeve (if needed)
• Scissors / Utility Knife: Cutting the Heat Shrink Tubing
• Heat Gun or Lighter: Applying Heat to shrink the Shrink Tubing

Grab the 22-Gauge Solid Hookup Wire and cut two segments to the desired length for your project.  For ease of identification, I choose Red wire to represent my positive lead and Black wire to represent my negative lead; each will be connected to their respective positive and negative battery terminals.  For both wires, strip the insulation roughly the length of the Coin / Button battery diameter you are using for your project.

Once the insulation has been stripped, twist the bare wire around the needle nose pillars in a circle so that it starts to take a spiraling shape.  The spiraling shape of these wire end bends will maximize the surface area between the wire lead and the battery terminal while providing compression tension to hold the wire leads in place between the battery terminal and Heat Shrink Sleeve.

I have found that 1-2 Heat Shrinkable Tubing (which shrinks to 50% of its original diameter when heated) works well for this scenario.  As a general "rule of thumb" when selecting a Heat Shrink Tubing diameter for this project, select a diameter that is 65% the diameter of the battery you are using if the battery height is less than 3.5mm; if the battery height is greater than 3.5mm, select a Heat Shrink Tubing diameter equal to the Coin / Button battery diameter.  Note that Heat Shrinkable Tubing is usually labeled and sold in pre-shrink diameters. 

The length of the Heat Shrink Sleeve, or a cut segment of the Heat Shrink Tubing, will also vary based on the battery diameter.  Typically a sleeve length of 1.5 times the battery diameter works pretty well to encapsulate the battery and wire leads.  Since the Heat Shrink Tubing is sold in long strips, it will likely be necessary to cut it with a pair of scissors or utility knife to the optimal length.

In my trials, I have found that the following batteries work well with the following 1-2 Heat Shrink Tubing diameters and sleeve lengths:

• CR2032 (3v 20mm × 3.2mm) – Heat Shrink Diameter: 1/2 inch; Sleeve Length: 1 1/4 inches
• CR927 (3v 9.5mm × 2.7mm) – Heat Shrink Diameter: 1/4 inch; Sleeve Length: Length  5/8 inch
• CR1025 (3v 10mm × 2.5mm) – Heat Shrink Diameter: 1/4 inch; Sleeve Length: Length 5/8 inch
• LR44 (1.5v 11.6mm × 5.4mm) – Heat Shrink Diameter 3/8 inch; Sleeve Length:  Length 5/8 inch

Once you select the right Heat Shrink Tubing diameter and cut it to the desired sleeve length, it may be necessary to stretch the internal diameter of Heat Shrink Sleeve slightly to allow the battery to fit.

First test fit the battery to see if you can get the Coin / Button battery into the Heat Shrink Sleeve without stretching it.  If stretching is required, I found inserting needle nose pillars into the Heat Shrink Sleeve and prying the handles outward gently to be an effective method of increasing the internal diameter of the Heat Shrink Sleeve.  Be careful not to over stretch the Heat Shrink Sleeve during this process; a little effort goes a long way, so just stretch it a little at a time until you can get the Coin / Button battery in with a snug fit.

When you insert the Coin / Button battery into the Heat Shrink Sleeve, position the battery slightly off centered between the open ends of the Heat Shrink Sleeve.  Because of the snug fit, it may be necessary to nudge the battery through the sleeve.  Pushing with the needle nose pillars, in the closed position, seems to be an effective method of advancing the battery within the sleeve.

When you are inserting the Coin / Button battery into the Heat Shrink Sleeve, it will be beneficial to note which battery sides are the positive and negative terminals.  It will be difficult to tell which is which once the battery is inserted in the Heat Shrink Sleeve.

With the battery positioned in the Heat Shrink Sleeve, we are now able to insert the previously prepared wire leads onto the Coin / Button battery terminals.  When inserting the wire lead between the Coin / Button battery terminal and Heat Shrink Sleeve inner skin, ensure you have the spiraling wire end pointing towards the battery terminal; this will reduce the risk of the wire ends from puncturing through the Heat Shrink Sleeve along with providing a slight spring tension when compressed.  If you positioned the battery slightly off centered in the Heat Shrink Sleeve, insert the wire leads from the side of the sleeve with the longer length; when the sleeve is shrunk, this will allow more sleeve to be wrapped around the wire leads. 

Also make sure that you push the wire lead through enough so that the insulation of the wire is leaning on the Coin / Button battery terminal; this will reduce the risk of the wire lead shorting the two Coin / Button battery terminals.  If you had specific wire colors designated for each battery terminal polarity, this is the time to remember which side of the battery is which in the Heat Shrink Sleeve.

Once both wire leads have been inserted and correctly positioned, gently squeeze the two sides of the Coin / Button battery to flatten the spiraling lead wire ends slightly.  You do not want to over squeeze since leaving some spring tension is desired to maintain a good mechanical hold between the Coin / Button battery, Wire Leads, and Heat Shrink Sleeve.

Once you are comfortable with the position of the Coin / Button battery and Wire Leads in the Heat Shrink Sleeve, it is time to apply some heat to shrink wrap it.  Although the proper way is to use a heat gun to slowly and progressively shrink the Heat Shrink Tubing, an everyday lighter works just as well.  If you decide to use a lighter, make sure that the flame does not touch the Wire Lead insulation or the Heat Shrink Tubing skins.  Make several evenly paced passes on both sides of the Heat Shrink Sleeve to ensure that you have sufficiently shrunk the sleeve securing the Coin / Button battery and Wire Leads.

After giving it a minute or so to cool, your assembly is complete.  At this point, I would recommend testing it with a multimeter to confirm the desired voltage and to ensure no shorts are present.

For added security, a small zip / cable tie can be used to apply additional compression to the heat shrink sleeve, wire leads, and Coin / Button battery package.

--Matt Royer