Power the nodemcu dev board

[TD-er]

You could search for a low drop voltage regulator and try to power it from 3V3.
But since it will be running of batteries, I assume you will probably also put the ESP into deep sleep?
Then the quescent current of those regulators becomes important.
Most of those dev boards like the NodeMCU boards have components which are not really optimized for low power consumption.
For example the AMS1117 voltage regulator, used on quite a lot of boards, may use 5 - 10 mA while nothing is connected to it.

If it is just about being portable and you don't really care about low power, then you can also look for something like this:
https://www.aliexpress.com/item/1005004864813782.html

These have a proper charging chip on board and a DC/DC step-up converter which can output a stable voltage regardless of the battery charge state.

[bidrohini]

Let me suggest an alternative but permanent solution. You can design a power supply board for NodeMCU like this.
https://www.pcbway.com/project/sharepro ... upply.html

[TD-er]

I browsed through the video a bit and at 5:12 you can see it is using just a 7805.

That's a linear voltage regulator, which needs at least a few V more on the input than the output. (7V minimum if memory serves me well)

So you might be able to use 2 batteries of 3.7V in series, but not in parallel.
However if the batteries get below 3.5V (total below 7V), the 7805 may get unstable.
Actual "undefined behavior" and minimum input voltage is depending on the brand of the regulator.
This means you can't use the full charge of the cells.

Also such a voltage regulator is quite inefficient (well it is efficient if you plan on heating stuff) as the current is the same for input as well as output. But since there needs to be a voltage drop, that drop times the current will be wasted as heat.

TL;DR
The 7805 is not the best one when powering an ESP on 3.7V cells.

[chromo23]

I can recommend the HT7333. I use it for all my battery powered projects. It only has a maximum output current of 250mA but i personally had never issues with it. It´s quiescent current is only 3.5µA....

[Micha_he]

I supply an ESP01 via 3 small Si-diodes connected in series (Vcc max ~ 3,3V). DeepSleep with 1-2 wakeup's per day.
3,7V/2000mAh = Runtime without recharging ~16 months

[TD-er]

I can recommend the HT7333. I use it for all my battery powered projects. It only has a maximum output current of 250mA but i personally had never issues with it. It´s quiescent current is only 3.5µA....

That seems like an interesting one.
Maybe you could place 2 parallel with some capacitor to be able to handle the extra (short) peak currents when starting WiFi.

However I can't find what the minimum voltage drop is.
Any idea how low this one can go and still output a stable voltage?

[TD-er]

I supply an ESP01 via 3 small Si-diodes connected in series (Vcc max ~ 3,3V). DeepSleep with 1-2 wakeup's per day.
3,7V/2000mAh = Runtime without recharging ~16 months

This also means you have quality batteries as some also would show self-discharge over such a long period.
Especially those with protection circuit built in.

[chromo23]

However I can't find what the minimum voltage drop is.
Any idea how low this one can go and still output a stable voltage?

I don´t know... but i measure the battery voltage (single Lithiumbattery) and log it.

Here the result:

Bildschirmfoto 2023-09-27 um 14.38.58.png (54.31 KiB) Viewed 1733 times

[TD-er]

Huh? so the chip seems to output even when the input voltage drops below the 3V3?
With linear regulators, you can only output less voltage compared to its input.
But the ESP8266 may still operate with voltages as low as 2.6V (not guaranteed it will work stable as the flash chip etc. also must support it)
So does this chip simply send out the input voltage when its input voltage gets below the target 3V3?

[TD-er]

Ah found a nice blog post about this: https://iotips.tech/ldo-linear-regulato ... 2-package/

[chromo23]

So does this chip simply send out the input voltage when its input voltage gets below the target 3V3?

So it seems

[chromo23]

Ah found a nice blog post about this: https://iotips.tech/ldo-linear-regulato ... 2-package/

I am not sure these measurements are completely true...It would mean, that with an input of 2.6 volts from the battery the voltage after the regulator would be lower than 2.3 assuming it only needs 50ma for the wifi.
I doubt that the esp8266 would still be able to work under this condition.