Restart when battery is dead and solar is connected

[realbeeit]

Hello,
i do not know if that is right but my boards die at battery level around 3.6 3.7V. When I connect charger via solar input and hit reset button it turns on. Is there any way if battery is dead and then solar is connected that board turn itself on without pushing reset. My boards are configured to deep sleep and boot every two hours but when battery is drained even 3.7v shoudnt be problem it turns of and never turns on by itself. Thanks.

[lewisxhe]

Solar energy cannot power the board, it can only charge the battery.

Is the voltage 3.7V the voltage when it restarts? Maybe the battery discharge current is insufficient when the modem starts, causing the voltage to be pulled down. Have you tried using a voltage regulator to adjust it to 3.7V for testing?

[realbeeit]

I am not saying that solar power should power the board, I know it is only for battery charging. I am saying that when battery is charged via solar panel device which was in sleep mode will not restart on its own.

3.695V is minimum voltage by battery I am using. I am using Li-Ion 10000mAh batteries. Maybe BMS of battery is blocking and providing insufficient current...

[lewisxhe]

In other words, the 3.7V board can no longer start? Can the red light on the modem be on?

[realbeeit]

It turns on and then turns off and trying to start again but is insufficient. After some time it just stops trying and then I have to connect solar charger and when I hit reset button it is working again.

[lewisxhe]

Can you connect an external USB2TTL to monitor the ESP32 serial reboot behavior? The reboot message contains the reason for the reboot.

[realbeeit]

I don't have that...

[lewisxhe]

This is not easy to do, I don't know the reason

[realbeeit]

I will get it and try.

[deeja]

@realbeeit - try a capacitor Xinyuan-LilyGO/LilyGo-Modem-Series#287 (comment)