Solar powered esp32

Discussion Projects
1

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.

Any advice would be most appreciated.

2

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).

Background: without the special module, the voltage of the panel drops as soon as there is a load. The module fine-tunes the load to keep the panel happy. Adafruit has a very nice article explaining the details: Design Notes | Adafruit Universal USB / DC / Solar Lithium Ion/Polymer charger - bq24074 | Adafruit Learning System. The second graphic shows how the voltage collapses already with only little current flowing.

3

Cheers for the heads up, I’ll have a look at the Adafruit module.

4

Yay a thing I made works. Has a 6v solar panel, waveshare solar management board, 1Ah battery and a esp32

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5

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?

More voltage or more current?

6

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.:

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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.

7

The waveshare can take upto 24v so i was thinking 3 6v panels at a total of 18v should be fine.

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