ESP8266 Community Forum

Around my house I have several esp-12 running with temperature (DS18B12) and humidity (SI7021) sensors on them. they run a http server and when I do a http request to them I get the temp/humidity values back in plain text.

I read the sensors every minute to store the values in a database. Currently all of the modules are powered from the mains, using 5v adapters and LM1117 to convert to 3.3v.

I was wondering what would be the bast way to make the same kind of sensor battery powered. I can of course use some aa batteries and the LM1117, but I'm guessing that's not the most efficient way.

What kind of batteries should I use (preferably rechargeable) and is there a way to monitor the battery life?
Is it even possible to get a proper battery life while reading the sensors every minute?

With batteries, don't use LM1117, since this LDO has a big quescient current, it will drain your battery even if ESP is in deepSleep().
You can use SPX3819, or even better HT7333 or XC6203 instead.

For a battery powered system, you are using the wrong network topology.
A sensor should not act as server, instead it should push its data to a server in regular intervals and use deep sleep between measurements. Also to increase battery life, you should increase the intervals and/or accumulate data by waking with RF disabled and sending the accumulated readings every hour or so.

As for batteries: there's a huge thread on this, which you should check out.

A few weeks down the road, and some ali-express parts further down the road, I'm picking this project up again

I'm switching the network topology so that the esp powered sensors will push the data and then go back to deep sleep.
I now have some CN18650 batteries that should be able to provide enough power to get the ESP going. I've also ordered a few HT7333 modules, since the battery could deliver 4.5v at full charge wich the ESP would not like.

One thing I would like to be able to do is check the battery life of the ESP, so that I can send a notification if charging is required. What would be the best way to do this? I can use a voltage divider to scale 4.5v down to 1v and feed it to the ADC, but I'm wondering if that would give me any usable readings. Any ideas?

lethe: Can you give me a link to that batteries tread? I'm unable to find it.