Replace batteries with low-voltage circuit... advice?

I have a number of 3v battery (2x AAA & CR2032) sensors now in most rooms, I’m planning to move into a new house soon and plan to run extensive networking cabling anyway and I’d like to also run some low-voltage 3v cable to power all these devices so I never have to change batteries in the sensors.

My initial thinking a fairly simple solution would be to run speaker wire to all the points where I’d like the sensors to be, and run them back to a central point where I connect them all to a 3v DC power supply which has multiple outputs.

Does anyone have any experience with this kind of thing?

Any recommended ways to do it?

Can it work with a ‘ring’ type wire which spurs off to power each device instead of individual lines to each device?

Is there some kind of 3v DC power supply which has multiple outputs I’m missing with my search?

I’m sure someone must have had this bright idea before me! :sweat_smile:

I have the CR2 eliminator cable with the USB end plugged into a wallwart with the correct voltage requirement in my setup for a switchbot bot that I use to toggle power to the port my skyconnect is plugged into so I don’t have to worry about battery replacement for it.

I did come across those, but the pricing was a little eye-watering for the number of devices I have unfortunately.

Was looking at more of a diy solution ideally to keep cost down.

You’ll need to size your cable adequately (cross-sectional area) to avoid too much voltage drop between the PSU and the farthest devices.

You may also need ferrite chokes to handle noise/interference.

Sure. This will probably save cable.

Probably not. It’s rare to distribute 3V. At any given power, the lower the voltage, the higher the cross-sectional area needed to avoid unacceptable losses.

Why do you need multiple outputs, anyway? Get a single 3V or variable PSU with adequate power, as efficient as you can afford, and go to town. Let us know how it goes.

I have some devices that I converted when I was using SmartThings:

To avoid voltage drop due to current through long runs of cable distribute a higher voltage like 12V everywhere then step it down to the required 3V or 5V at the room it is needed. There are loads of buck converter modules available for this.

Make sure your 12V distribution is protected with fuses or DC circuit breakers.

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You don’t need multiple outputs, just add a screw connector big enough to fit all your wires. If you have all “normal” sensors, you can wire them in star or “ring”, the current is so low you probably don’t have big voltage drop (bigger than half-discharged battery voltage drop would be). Of course use decent wire size.

Plenty of options on AliExpress, eg. CR2032 3V Battery for CR2032 Powered Devices
https://a.aliexpress.com/_EH6T6IG