ESP8266 Community Forum

- Tue Sep 20, 2016 5:18 pm #55447 I've been running my ESP on solar power. (Arduino programmed). The sketch runs for 1 minute and sleeps for 4 minutes. My board uses a 3.3V MCP1825 voltage regulator with a minimum V rating of 2.1V.

Recently, I was testing how long it would run on a 18650 battery. I'd run until the battery went flat. After a couple of tests I bricked my ESP. Serial shows a constant ...

Fatal exception (0):
epc1=0x4021a4d4, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000
Fatal exception (0):
epc1=0x4021a4d4, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000
Fatal exception (0):

The voltage regulator is OK - the problem follows the ESP.

So my questions are:
Does the ESP8266 have BOD capability? If so, how is it set?

Is it known that running the ESP below it's minimum voltage (1.7V) can cause this?
(i.e. Did I just have bad luck?)

If there is no BOD, and running too low can brick the ESP, I guess I'll have to add a voltage monitor circuit.

I'd appreciate any experience or thoughts on this.
Thanks, John

- Tue Jan 17, 2017 12:31 am #61116 Late reply, but here goes...

You should never run an 18650 battery until it "goes flat". That will destroy it, and if you try to charge it from flat at normal charge rates, you might end up with a chemical/electrical fire on your hands.

Always run it via a battery protection circuit. There are plenty of combined charge/protection modules available on aliexpress that use the TP4056 charge controller and DW01B protection IC that monitors the voltage of the 18650 and disconnects it from the load once it goes below 3v.

This 'ere's the kiwi, the emblem of our land, you can stick it in a bottle, you can hold it in your hand.

- Tue Jan 17, 2017 2:44 pm #61151 Unfortunately, I have no control over whether or not the user runs their battery flat or even how they configure their solar charging system. However if they brick the ESP it becomes my problem.

So the real question for me is does the ESP have BOD as most microcontrollers have, and if so, how is it setup.
Thanks for your input though.

- Tue Jan 17, 2017 6:43 pm #61160 No Brownout hardware inside ESP8266. + Don't forget minimal voltage for 'sister chip' = SPI Flash Memory
In my case i put ESP8266 in permanent deepsleep mode if Vbatt is under 3.0V : good for ESP8266, Flash memory and battery.