ESP8266 Deep Sleep Energy Saving

After reading many post of people getting months of ESP8266 running time off batteries I decided to set up my own to see why my battery life was terrible:

Parts:
Node MCU ESP8266 (CH349G Serial Chip, AMS1117 Voltage Regulator)
LiPo Battery: 2S 850mAh (7.4V)
ADS1115 ADC (to measure voltage, 500K Voltage divider)

Test setup:
Two ESP8266 setups were completed, one ESP was standard and the other had the LED and Serial Chip disconnected to conserve Battery.

Test Program:
ESP Wake every 20 seconds (with radio disabled)
Take voltage reading and store in RTC memory
Deep Sleep
……………………………………………………………..
Every 5 minutes (15 wake cycles)
Take voltage reading
Connect to network and transmit all data to Influx Database.
Disconnect from network
Deep Sleep

Results:
You can see from the below screenshot the battery voltage over the duration of the test:

Unmodified ESP8266:
Time from 8.36V to 7.28V (97% to 7% of Li-Po capacity) was 87hrs and 20mins (3.6 Days)

Modified ESP8266: (No LED or Serial Chip)
Time from 8.36V to 7.28V (97% to 7% of Li-Po capacity) was 101hrs and 16mins (4.2 Days)

Conclusion:
Months of usage seem far from achievable with a minimal setup and all precautions taken. Actually the ESP seems pretty unusable on a battery for anything more than a measurement every few hours.

Further Improvements:
The stock voltage regulator is a known power drain, an alternative is recommended but I did not get around to that yet.

That’s it!

InfluxDB Backup Database (2 methods)

It makes sense to periodically backup InfluxDB to an external drive in-case of corruption of onboard memory. I am using a USB memory stick.

A simple cronjob can take care of this (every night 2am), open Crontab:

sudo crontab -e

and insert the below line: (change for your storage device)

0 2 * * * influxd backup -portable /media/usb/drive

Backup names start with the date it was generated but it can get messy after a few weeks.

Long term its better to run a backup script to put backups in individual directories and catch errors etc., create a python file for this and use the below example:

nano /home/pi/influx_scripts/influx_backup.py
import os
from datetime import date

today = date.today()

d1 = today.strftime("%Y_%m_%d")
print("Date", d1)

command = "mkdir /media/usb-backup/" + d1
#print(command)
os.system(command)

command = "influxd backup -portable /media/usb-backup/" + d1
os.system(command)

command = "kapacitor backup /media/usb-backup/"+d1+"/kapacitor.db"
os.system(command)
os.system("echo Backups Done!")
sudo crontab -e
0 2 * * * python /home/pi/influx_scripts/influx_backup.py

You can keep an eye on the USB memory stick size by the below snip of script which can be logged to InfluxDB. A Grafana alarm keeps an eye on the size and alerts if getting close to capacity.

DIRECTORY="/media/usb/drive"
if [ -d "$DIRECTORY" ]; then
    usb_mem_usage=$(du -s $DIRECTORY | awk 'NR==1{print $1}')
else
    usb_mem_usage="-1"
fi
echo $usb_mem_usage

All done!

Setup HTTPS for Grafana

By default Grafana operates over HTTP but for added security you can operate over HTTPS. For my use case I am using a self generated certificate as not using a public domain.

Generate Keys: (a key.pem and cert.pm files will be generated)

openssl req -newkey rsa:2048 -new -nodes -x509 -days 3650 -keyout key.pem -out cert.pem

Put the keys in /home/pi/ directory. It did not work for me in the /etc/grafana/ directory.

sudo mv cert.pem /home/pi/
sudo mv key.pem /home/pi/

Change permissions of the keys:

sudo chmod -R 777 /home/pi/cert.pem
sudo chmod -R 777 /home/pi/key.pem 

Edit Grafana Config File:

sudo nano /etc/grafana/grafana.ini

Ensure the server protocol is updated and the key locations listed:

[server]
# Protocol (http, https, socket)
protocol = https

# https certs & key file
cert_file = /home/pi/cert.pem
cert_key = /home/pi/key.pem

Reboot system and all done!