What is it?

Makers, hackers, prototypers - we often cobble together a system from existing parts on hand, or spend some time analyzing a system and need to get our fingers (and test tools) inside the gear. These little "dummy-batteries" make a bunch of things easier for us.

Note: see AA, AAA and CR2032 coin-cell versions in my Tindie store.

Hack a battery pack - Say you have a 4-cell battery pack, but your circuit only needs 4.5 volts. Four cells (4 x 1.5) is nominally 6Volts, but replacing one of the batteries with a shorted-out dummy will give 4.5V instead. Short out two positions for 3V etc.

Analyze a circuit - Perhaps you have a device running on a two-AA battery pack and you want to measure the current. Use a 3-cell pack instead, and replace one battery with an open-loop dummy. You can put your meter in series easily to test the current consumption.

Inject external power - Maybe you have a device that uses up expensive batteries and you want to use a wall-wart supply instead. Use an open loop dummy battery, plus a shorted cell in a two-cell pack which lets you inject external power. [CAUTION - don't mix external power with an actual battery]

Analyze a prototype's behavior - to analyze the operation of a device as the power fades out, or perhaps to chart power usage in different operational modes, use an open loop dummy battery (and shorted ones for any other positions) and you can use a combination of external power, volt meter, ammeter etc to do a thorough analysis.

Why did you make it?

In many situations I found myself soldering up test wires on new prototypes. With a couple of dummy cells I could switch quickly between test and operational mode with my projects.

What makes it special?

Its simplicity is what makes it great. No fancy components or complex hook-ups, just pop it into your existing gear without wasting time.

Pre-wired or do it yourself?

You can select pre-wired units, or you can thread the wires through yourself. If you get a pre-wired one you can of course snip out the wires and reconfigure it anytime you want as well.

Simply use the pull-down to select one of the pre-wiring options. It's a little fiddley to get the wire into place, but with some effort you can do it and save a dollar. If you have stubby fingers from a long career playing the saxophone, you might want someone else to thread it for you. ;)

Caveats

It's pretty simple and obvious how it works, so common sense will probably be all you need to be safe. A few warnings are probably in order.

• The cells are wired with 22 - 24 AWG wire, which would technically have a maximum current of 3-4 Amperes. The wire would be getting hot at that level, so best not to push it for fear of melting through the plastic.

• It's a 3D-printed part using PLA filament which gets soft at high temperatures above 70C, so you probably don't want to use this in a hostile environment.

• Don't mix an external power feed with a real battery. That's dangerous

• Do not swallow