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I have an application featuring the ESP8266 and I am trying to figure out the best but more important right way to power it. The ESP is the only main load in my application, its current draw will range from 20uA in deep sleep mode up to around 150mA when the RF calibration takes place.

I am planning to use either a LiPo or LiIon battery so the voltage of one of those cells will range from like 4.2V down to 3.0V. It is really important that the draw does not exceed the 20uA by much when the ESP is sleeping, since the circuit is supposed to be running for about a year on one charge.

I tried LDOs like for example the MCP1812 rated for 3.3V fixed output and it actually worked. But I think I used the device outside of its operation range as soon as the battery voltage was 3.3V as well. I am not sure about switching supplies or LiPo charge controllers, are there any that have built in regulation and are super efficient? I think I need a charge controller anyways to provide necessary protection to the batteries. Anyway, this is a field I am not familiar with and I am curios what are the possibilities here.

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  • \$\begingroup\$ Well, if you want run MCU on 3v3 and discharge a lipo down to 3V you must use a switched converter. There is a chance to discharge lipo down to 3v4 only and use LDO with 100mV drop, or run MCU on 3v0, 2v7 etc... with appropriate linear regulator. \$\endgroup\$
    – user208862
    Commented Apr 26, 2021 at 3:28
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    \$\begingroup\$ There are plenty of swithed regulators chips with quiescent current of 10th uA usually, so choose the one with low input voltage (not like 30v or higher) and suffiecient output current. \$\endgroup\$
    – user208862
    Commented Apr 26, 2021 at 3:40

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Take a look at the amazing Energizer Ultra Lithium AA cells...

https://data.energizer.com/pdfs/l91.pdf

Not only do they pack a whopping ~3500 mAh capacity at low current drains, they also have extremely low self discharge rate so can last decades.

But best of all, at low current draws they output a voltage in the range of 1.8 - 1.4 V up until the very last moment before they die...

enter image description here

This means that you can depend on two of them in series to give you 3.6-2.8 V throughout their extremely long lives.

This almost exactly matches up to the ESP8266's is rated voltage range of 3.6 to 2.5 V... enter image description here

...so you can very efficiently connect the two AA's directly to the ESP.

For maximum battery life, it is also a good idea to add a decoupling capacitor across the power lines to soften the surge during the brief moments of high current draw - like when you are doing the RF calibration.

Depending on what percentage of time you spend in sleep versus wake, it is possible to make a system powered like this that runs for decades on a single pair of batteries.

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