ESP8266 (ESP-07) Power Management with AA Batteries and BMS Chip Integration

Question

Hello! Popular situation, I would like to make an IoT chip based on esp8266 (ESP-07 must be the one) I would like to power it from AA batteries of 3, standard configuration with ldo MCP1700. There are many projects like this, but I have not found enough information on what to do when the...

tos18 · Accepted Answer

You have an ADC in the module - you can use it to measure the battery voltage (you will need a divider)- the rest in the software. You can even cut the power with one of the outputs.

Anonymous · Accepted Answer

. It will not damage itself. It can reboot and if the voltage goes lower it will shut down. . The datasheet note for the ESP8266 states: 2.5V ~ 3.6V. You already have . . Provided that this ADC is calibrated. The characteristics of this ADC in the ESP8266 are highly non-linear. . Yes.

tos18 · Accepted Answer

Fortunately, we don't need a super accurate measurement. It's just a matter of finding out that the battery voltage has reached the value at which you need to go to sleep (light the [LOW BATTERY] lamp, etc).

Anonymous · Accepted Answer

. There is a link in my footer to a post with Kolban's book for ESP8266 attached. Well worth a browse. As for the battery voltage measurement circuit itself, there is an interesting project at the link below. It is better to measure this voltage via the ADC in the ESP at half the battery voltage. Added after 28 [minutes]: . Here you have an explanation

Anonymous · Accepted Answer

Just don't forget that the ADC range is up to 1V. So the divider would have to be quite a bit bigger....

Anonymous · Accepted Answer

. Actually in the bare ESP8266EX this will be the case and you have to be careful not to exceed the 1V value. In modules like Wemos or NodeMCU there is already an internal divider and then the range is up to 3V3.

tos18 · Accepted Answer

There is no divider in the esp07 so you have to be careful as with the bare 8266.

Anonymous · Accepted Answer

It's not so bad, gentlemen, nothing will happen to you, the pin tolerates more than 3.3V, but the reading will be poor because the range is up to 1V, so voltages higher than 1V will already be a constant, probably max1024. Considering what the author wrote 3 batteries is 4.5V so the divider would have to go down to 0.8V

Anonymous · Accepted Answer

Well you have asked a basic question and I will add more. If I use an LDO it will not put the circuit to sleep at 3V on the battery but at least 3.5V.... You have to take into account the dropout from the stabiliser. So if he feeds the LDO with 3V, the esp will get 1.8V ... So that and behind the LDO below 2,6V- we put to sleep. Because the dropout on the battery will also be behind the LDO. Although I do not hide that there are better stabilisers but hard to find and more expensive dropout at 100mv level.

TvWidget · Accepted Answer

. Usually the batteries are replaced with new ones. For what reason do you want to cut the power ?

Dawidixxx · Answer

That's right, but if I'm not mistaken, by enabling the deep sleep function permanently (for manual reset), the RTC clock module continues to work which means that the board still needs a 3V power supply after all, and as I mentioned it may not work :/

Dawidixxx · Answer

Hello there General khoam Thank you for writing back, as always you are very helpful . Please forgive me, but I had to. Thank you also tos18 for your pertinent comments . Very important information, I would love to read the recommended book on the ESP8266 module, supplementing the information on resetting, disabling. Well I read the catalogue note (probably the latest one) and found out about the newer versions with the note EX (from 2.5V) however I thought that the older versions e.g. ESP-07 -01 do not have it I purchased a couple of ESP-07's from Ali because of the antenna, which I also want to do some research on as to range and power taken. The thing is, I don't see this note on the boards I bought, unless it's another thing I don't understand and the EX add-on doesn't introduce a lower power option, just the esp8266 version itself. Well I wanted to use the ESP-05 module with the ex annotation as a design enhancement later. Yes, I have read that I need to calibrate the measurement obtained from the voltage divider (I need to read up on the built-in resistor) I apologise for not being very accurate, however I have over a year to write my thesis and I am doing research, I am very pleased with the interest about this module on the forum (strangely the professors at my university have only heard a little about it 0.o for that we have stm32f429 boards that people can't grasp, and the detail that we won't even use a quarter of their power :/)

Dawidixxx · Answer

Jarzabek666 Are you proposing that the maximum voltage should be 0.8V? well i tested the values 200Kohm/45Kohm (for low current, maybe i will give even more) Is this for safety reasons or did I misunderstand? (since I could set 4.5V as 1V, the excess will be treated as 100% if the pin tolerates 3.3V)

Anonymous · Answer

This is how I suggested that the program should see higher voltages above 4.5V, because as far as ordinary batteries are concerned, one working battery has 1.6-1.7V or even 1.8V which would give us 5.4V. . Yes and you won't see it in the program that's the point, voltages higher than 4.5V it will already see as 4.5V with a 4.5/1V divider . With your 200/47Kohm divider there is quite a safety range as the supply would have to exceed 18V to damage the ESP. I mainly wrote this way so that you would see some spare in the program more. On the other hand, I don't know why you would bother with it if esp8266 has a power supply of 18V to damage ESP. I don't know why you bother if the esp8266 has a VCC voltage readout. see the ESP.getVcc() command....

Anonymous · Answer

. What if it doesn't manage to read the voltage with this method? This is already behind the LDO.

Anonymous · Answer

Whatever the combination, measuring the voltage directly at its source, i.e. the battery, is the safest way. In this way, you may also be tempted to measure the drop in this voltage as a function of time, i.e. to roughly determine the quality of the battery.

Dawidixxx · Answer

TvWidget I didn't know what could happen if the batteries discharge to a very low level, that the esp8266 gets below 2.5V As I mentioned this is an issue for an engineering paper and everything has to be right, I thought the chip could break down. I found out here that the chip has protection, i.e. it will first reset, then shut down. Initially I wanted to add a BMS with 18650 (cut off at 2.5V), given the LDO dropout, maybe before the chip itself? However, this is where two issues remain, either I add this BMS, just need to see how much current it draws during deep sleep operation, and if I don't use protection, I need to find information from the manufacturer or in some book that the circuit will react e.g. to 2V 1V ~0 and won't damage itself I need to read the datasheet note again carefully. Ps. I remember about full sleep, i.e. on maximum sleep, the chip will wake up after ~3.5h - the internal RTC clock is running With ESP.deepSleep(0) does it still work? it shouldn't in my opinion Jarzabek666 You have provided . That's quite a drop, in the catalogue note I saw ~ 178mV I checked it myself a while ago and at 3V input I got 2.5V at 70mA (motor) (I didn't have such a large capacitor, I used a smaller one, the kit is already coming to me) Did I miss a pattern? Thank you all again very much for your interest .

Anonymous · Answer

Sorry, I didn't read that it was an MCP1700, I thought it was a standard LM1117.

TvWidget · Answer

Too low a voltage will not damage the circuit. You do not need to worry about this. You should, however, consider whether frequent resets will cause any problems due to the functionality of the device.

Anonymous · Answer

. The RTC and some of the memory associated with it works, but if you use ESP.deepSleep(0) then the RTC itself will not wake up the chip. According to the documentation: To put the ESP8266 in deep sleep mode, use ESP.deepSleep(uS) and pass as argument sleep time in microseconds. GPIO 16 must be connected to reset (RST) pin so the ESP8266 is able to wake up. . Specifying a value of 0 in ESP.deepSleep() will result in this being treated as 'infinite' time and the chip can only be woken up by reset. This is explained in detail at the following link: The attached manufacturer's document describes the sleep modes in detail. The examples given are based on ESP-IDF commands, but you can also use them with Arduino HAL.

ESP8266 (ESP-07) Power Management with AA Batteries and BMS Chip Integration

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