Im currently putting together a shopping list for an solar powered esp32 temperature sensor for the greenhouse. I already have the esp32 and a BME280.
I currently have in my basket the following:
3.0v solar panel
LiPo Amigo pro (or possibly waveshare solar power management module)
2200mAh lithium battery 3.7v
The plan is that the esp32 will take a temperature reading once and hour push it to a sql database, then deep sleep. This will run off the battery and then the solar will charge the battery.
Skip the Amigo Pro, and buy a solar power management module. I don’t know the waveshare module, I have one from Adafruit (they have two, the newer one is better and cheaper).
Right I think I need to get some more PV panels as the single one I have doesn’t seem to be capturing enough power to charge the battery and keep the esp32 going even though it only pings the temp once an hour then goes into deep sleep in between.
Question I do have my current solar panel is a 6V 150mA 0.75w panel 80mm x 80mm.
If I was to get another two should I wire them up in serial or parallel? What is better for charging my battery while running the esp32?
In my experiments, I have found out that voltage is the problem so I decided to wire them up in serial.
But you have to check the waveshare module. The (newer) Adafruit module takes up to 10V input, so theoretically two 6V modules are above specs. In full sunlight, that is definitely too much.
I would suggest that you get yourself an INA219. This is a very cheap chip that measures voltage and current. If you put it in between the waveshare and the solar-module, you will see how voltage and current change over time. E.g.:
This is a single module at the end of charging. You can see that it actually delivers more than 6V in full sunlight. Charging is down to 14mA (46mA-32mA), and when the charging circuit decides that the battery is full, the current drops to 32mA (that is the idle-current of my mcu).
Ideally you would need three INA219: a second one between the waveshare-module and the battery and a third one between waveshare and consumer. I did my measurements one after the other.
@BnEc, some time has passed since your last past. Have you gotten new insights into operating an ESP32 on solar cells? E.g. seasonal changes, battery sizing and so on?
It be great to hear from someone that has operated a solar ESP32 through summer as well as winter (from your German language interface settings, I’m assuming your solar ESP32 runs in Central Europe – edit, no, that was @bablokb’s interface).
To be honest the ESP32 worked a treat in it’s low power mode in full sun. However I took apart the set up some time last year with a view of doing something to it, though then my life took a sideways journey, so I’m afraid I’ve not got much more details recently. I plan on putting it back together and trying again soon. I’ll either post in this thread or create a new one when I do. I’ll make sure to mention you when this happens.
So after your comment, I went back to the project, to work out if there was something wrong as previously it would work for about 5 days and then die. I realised my mistake was in wiring the solar panels in series, when in actual fact I needed them to be in parallel.
Today I have rewired the panels and finally properly wired in the 5v and GND wires to the esp. It’s now working a treat.
