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Comment by bsilvereagle | Hacker News Reader

How're you powering the ESPs? It sounds like you have them distributed quite a bit. Are you running coin cells? Dedicated 5V wall warts?

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Most of mine are just using little wall-warts through micro-USB cables. The star-tracking camera mount (which I even lugged up a little foothill for the eclipse), is battery powered, usually using one of those USB battery packs designed to charge phones. I can also hook it to my deep cycle battery when I'm camping or whatever through a small 12V -> 5V circuit (it's used for other things too). ESPs do have super low power modes for things like the door sensors that only need to do anything when they're triggered an for those you can power them with lithium batteries for pretty long times.

Coin cells are not an option- it consumes around 200-300mA while actively transmitting, and around 10uA in (one of) sleep modes. I'm powering my custom temperature/humidity sensors with 18650 lithium batteries. I'm getting around 3-4 months of battery life with 3000mA batteries (waking up every 15 minutes to make a reading, associate with AP and transmit data to local influxdb server (which also runs Home Assistant to see the readings and control some AC outlets).

It may be an option if using (super)capacitors and only transmitting / receiving for a short fraction of time.

https://hackaday.io/project/28527-solved-esp8266-powered-by-...

Do make sure to check the leakage specs on a supercap, though. They tend to have pretty high leakage current, which may clobber your power budget in low duty cycle applications.

I stand corrected. By combining that with low-leakage wakeup timer ICs and low-leakage supercap, one could indeed design a device that runs for months on a single coin cell (transmitting every few hours).

Is your project open source. I've been wanting to build that exact sensor network for a hunidor

It is now: https://github.com/festlv/esp32-temperature-humidity-sensor

One option is to use 3.7v lipos[0] with a regulator[1], which can be done pretty cheaply:

[0] https://www.aliexpress.com/item/10pcs-3-7V-260mAh-Lipo-Batte...

[1] https://www.aliexpress.com/item/5pcs-Ultra-mini-DC-3-7V-4-5V...

Funny that I buy those exact same LiPos for my quadcopters, and never considered using them for an ESP8266. How much time do you get out of those if you're using a DHT22 sensor?

Funny enough, a battery-powered DHT22 is my next project, so I don’t know yet! But in my other experience the expensive part is powering on the radio, which spikes to 200-300mA at startup and then will sustain around 80mA as long as it’s on.

Well, I'm running a test with 2xAA batteries. With a modified version of https://github.com/rcarmo/azure-iot-esp-01-minimal-cpp that only wakes up every 15m to send a single multicast packet and the power LED removed, the battery's still at 3.08V after two months :)

Wall warts. Most of mine are deployed in places where recharging a Lipo would be a nuisance.

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