A dummy coin-cell (updated), this replaces a CR2032 coin cell in your circuit-under-test. Something I designed and use to solve a particular challenge – a simple, yet rather precise little item that makes a tedious task like injecting external power or measuring current much easier.

See also my AA and AAA surrogate batteries in my Tindie shop

What is it?

It's a simple dummy coin-cell that allows you to test a circuit without soldering or rigging up awkward wires another way. In a new custom circuit, you might have a surprise short that you might not notice when you power up with a real CR2032 coin cell. But with a current-limited supply you can catch it before it becomes a problem. You can also easily use it with a meter in series to test the current consumption of your device or circuit. A simpler application is using one to power a circuit from another battery pack, maybe to provide longer life. It's great when your device is in an awkward location. I use one in a garage-door-ajar indicator, for example. It's a handy little thing.

A 3D-printed disc of precise size, with a copper wire-threading route that covers all the key contact points that various coin-cell holders need. (There are many different battery-holders on the market, so you may need to rotate the dummy cell a bit in the holder to get optimal contact).

While precisely a CR2032 size (20mm x 3.2mm), in many coin-cell holders you can squeeze it into a CR2025 or even a CR2016 holder, as the 20mm diameter will fit as long as there's no thickness barrier. Useful in many situations!

Update - A small tweak to the design ensures there's conductivity at the centre of the negative side. Have noticed some coin-cell holders have a contact in centre rather than just a large pad. This should help those situations. (See photos)

Why did you make it?

I needed to test current consumption in a battery-powered device. Later I wanted to rig up a longer-lived battery supply (eg AA cells) instead of the coin cell. This 3D-printed little item let me do those things quick and easy. See the image of it in a small calculator measuring a 10 micro-amp current draw.

What makes it special?

It's easy to use and understand and solves a problem that is a bit fiddly any other way... and for very low cost. There are likely other uses I haven't thought of yet. Positive contact on one side plus the edges, negative on the other, just like a real coin cell. The alternative test situation is to solder wires onto your board, or using awkward clips that are difficult on small circuits, or which require disassembly. With this little dummy cell, you just slide it in and you're in business. Shipped pre-threaded with 24AWG wire and 10cm (4") long wire tails, so you don't have to do the fiddly bit.

The item will be either grey or white in colour, depending on stock.

Extended Version?

Some owners of equipment with difficult-to-reach coin cell locations expressed an interest in an extension version of this project, where a coin-cell holder is wired up to allow easy battery changes without disassembly of their systems. See my extender project if you would like to buy a wired solution to that particular challenge.