Chemmex, thank you very much for the many suggestions.

The twilight circuit seems to work. I will keep it monitoring to see if it is stable in the long run.

Maybe I have to buy a bigger solar panel.

I have already implemented deep sleep and it's working well, when the ESP is properly powered. My system is powered by a solar panel. The problem is how to make the ESP boot well, when the battery is discharged (if it happens at night) and then the sun is coming back. If I connect directly the solar...

The small UPS board seems to work better than the TP4056 with regard to the clean shutdown issue of the ESP. When the battery has not enough power to keep the ESP working, the UPS board provides ~0V, so the ESP is shutdown well, without going into a zombie status (due to low voltage). However I stil...

I am now trying a different approach. Instead of using the TP4056, I am trying to use this small UPS board:
I will see if that can solve the boot and shutdown problems related to low voltages at ESP.

TD-er wrote: ↑22 Jan 2022, 10:03 You can also add a capacitor over the EN and GND pin of the ESP.
This will delay the power up of the ESP to give the DC/DC converter some time to stabilize.

I am using a wemos d1 mini. That board does not have an EN pin, as far as I know.

Below the 'Post a reply' text area, there are 2 tabs, Options and Attachments. There you can select the file you want to attach. After adding a file, there is a button 'Place inline' that inserts a reference to the file in your reply, at the current cursor location: Oh, and the 'Delete file' button...

If you have charged the battery to 3.5V, you can connect the Wemos directly without DC/DC to test if there's enough power to start up the ESP. Just to make sure your battery is capable of the required current in that state of charge. Healthy 18650s can drive the ESP down to 2.8V. Also there is poss...

Now I turn the ESP "on" by connecting it to the output of a DC/DC converter that has an "EN" pin. That "EN" pin is controlled by the CN302. I found that the "EN" is at ~3.5V so it enables the output of the DC/DC converter, but the output voltage of the DC/DC c...

I didn't solve yet the problem of the exact rising and falling threshold voltages for CN302, but I have found another problem. Even if I can control the enable of the DC/DC converter --> wemos exactly at 4.0V, the battery cannot be charged enough to provide enough current to the wemos. So the ESP ca...

Yes, it is the same datasheet: http://www.consonance-elec.com/pdf/datasheet/DSE-CN302.pdf I am implementing the schematics on Page 2, Figure 1. The Vbat is the voltage taken directly from the + head of the battery (18650). Yes, your calculation is correct. I am expecting the rising threshold at 4.0V...

I will try to buy and use CN302. According to the hysteresis formula on page 5 of the datasheet, I calculated the following resistances for a hysteresis from 3.3V to 4.0V: R1=253k R2=121k R3=26k Do you think that those values are reasonable? I am using 3 potentiometers to set R1, R2, R3 exactly as ...

ok, I understand

Thanks all for the many suggestions. I will try them.

Do you have any suggestions about how to use SMD components (such as the CN302) with the breadboard?

There's a battery monitor IC from chinese Consonance Electronics called CN302. It can be used to cut off the load (or shut down the ESP if connected to the EN pin) when the battery voltage drops down to the limit set by resistor divider. It also provides adjustable hysteresis to allow the battery b...

According to the datasheet, it seems that also NCP304 can be configured with additional hysteresis. See page 17 here: https://www.onsemi.com/pdf/datasheet/ncp304-d.pdf

But I didn't understand well that example and how much the hysteresis can be extended.

Thank you, for all the suggestions.

Thank you, TD-er. Before using your suggestion (a FET to switch the power of the ESP), I would like to know if the following idea makes sense. I am thinking to use a NCP304LSQ33T1G (3.3v voltage detector) to monitor the battery voltage. The output of this voltage detector will be connected to the &q...

I have the same problem: wemos d1 mini (esp8266) does not wakeup after complete discharge of the battery. The battery (18650) is charged by a solar panel with a TP4056 module that is connected to a 3.7v to 5v dc-dc boost converter, that is connected to the 5v input of the wemos d1 mini. After the ba...