Originally shared by Gordon McLellan
My latest ESP8266 battery experiment platform. Here’s an ESP-07 connected to a single 18650 cell through a combination usb charging + protection board, as well as a 1N4001 diode. The idea with the diode was to use the 0.5v drop (at this low current) to protect the ESP from the 4.2v charging voltage.
The ESP-07 has an always on power led which I didn’t de-solder. I’ll get rid of it next time around. Oh, someone suggested earlier that I power the DS18B20 off a digital pin, so I’m trying that. GPIO5 powers the probe and GPIO4 reads it.
The cell I’m using is a counterfeit sourced from ebay. The seller proudly claims 5000mAh from one cell, ya, right. It weighs a fraction of what my genuine Panasonic cells weigh, and feels like it’s hollow. I guess that could be plastic case versus metal case, dunno.
Nice. I have a tip for you @Gordon_McLellan , while looking at a local tech store yesterday I stumbled upon some of those phone “power banks” for emergency charging your phone via USB. And it got me thinking. Since they are rechargeable, and could be used to power the ESP-12E/F with an uUSB loading circut. It could be a very cheap alternative since these pover banks are ofter dirt_cheap. I got a 2600mAh yesterday for $12.
I have tried using power banks, two different designs. The problem I ran into is the auto-shutdown circuit. As soon as the esp goes to sleep, the shutdown circuit turns off the power. Bypassing the shutdown circuit would bypass the protection circuit as well. I imagine there’s power banks that are always on, just a matter of finding one.
Aaaah, didn’t realize they did that. Will see how this one acts then.
Btw, regarding the esp’s sleep “cycle”, how does that work anyway? I read that you read and send a value every fice minutes then go into deep sleep in between. How do I accomplish that? Where can I read up on that? As I understand it I would need some sort of WDT to wake it up?
And how about MQTT messages sent from a brooker? How would the esp act upon those when received in deep sleep? Is the TCP/IP stack “alive” in this state?
Check out the arduino sketch and schematic here: https://github.com/gordonthree/batTemp
Sleep is achieved with a simple command, wake-up is achieved connecting GPIO16 to REST As far as I know the only thing active while ESP is sleeping is a timing circuit counting down the ticks you programmed with the sleep command. All the ports go high-z and program execution stops.
MQTT allows for messages to be queued and delivered when a device is available. I haven’t played with that feature much. Check out @Peter_Scargill 's blog… he has tons of great info on ESP, MQTT and much more. http://tech.scargill.net/
@Gordon_McLellan Thanks again for excellent assistance! 
[Master Yoda] Friendly community this is …[/Master Yoda]
Two days is all I got from a fully charged counterfeit 18650. Apparently the protection circuit isn’t working either, as the ESP has run the cell down to 2.19 volts!
