If you work with ESP8266 or ESP32, you will know that you cannot easily power it directly from LiIon without additional hardware. The default 1117 regulators on these boards are awful, having about 1V voltage drop from input to output - not only does it make those regulators very inefficient, it also means that, at top voltage of a LiIon cell under load (~4.1V), the 1117 regulator will already not have enough voltage and will make your ESP brownout all the time (especially when flashing). So, if you want to power an ESP8266 (or ESP32) from a LiIon cell, the most popular option are to either use a different regulator, or add some kind of step-up to i.e. 5V - only to step it down to 3.3V right after.

This AP2114 regulator is pretty much one of the best options available, as well as the cheapest one. At the typical voltage of a LiIon cell (3.6V-3.7V) and powering an ESP8266, this regulator will be about 94% efficient - making it as efficient as a typical switching DC-DC under the same conditions. I've tested it in my own projects and it works at 3.5V VBAT while outputting 3,3V at about 300mA - enough for an ESP, large display and some peripherals. Oh, and it's low-noise - for all your ADC needs.

Best part? This regulators has the same footprint and pinout as the cheap "1117" regulators used on all these ESPs. This means - you only have to unsolder the cheap regulator and solder this one in its place, something you can easily do with a soldering iron. In other words, this is the easiest way to mod your NodeMCU board so that it works from a LiIon battery!

So, if you want to make more ESP-powered portables, this is exactly the regulator you need to use. For one dollar, you get 3 of these - just add them as an extra to your order and you won't regret it. My profit here is small, about 10 cents per regulator after all fees - I'm more interested in making this awesome regulator known and available to people than making money on them.

I buy these regulators from a local reseller - they're cheap there, and they order them from TME. This way, I can be sure I'm buying genuine regulators and not something that's a re-marked 1117 and will completely fail when powered with LiIon, and when you're buying this from me, you can also be sure.

Q: I like this tip but I don't want to or cannot buy these from you.

A: That's absolutely fine, you can also get these on eBay/Aliexpress for a similar price! One thing you need to make sure about is that you get AP2114H and not AP2114HA - the HA, while having the same SOT223 package, has a different pinout and will destroy your ESP if soldered in place of an usual 1117. This is because the 1117-33 and AP2114H have a GND-VOUT-VIN pinout and the AP2114HA has a VIN-GND-VOUT pinout (which is more 7805-like), the two pinouts being quite incompatible. If, however, you got a AP2114HA, you can still use it - just shift the IC to the left by one pin so that the GND and VOUT pins match, then wire the VIN pin with a short piece of wire.

Q: Can't you power ESP directly from LiIon? While the datasheet says 3V-3.6V, people have it working when connected directly to a LiIon cell.

A: While it is possible to do that and I know that people have done this on ESP8266 throwies, it will only work for you under limited circumstances. First of all, this doesn't allow for 1) charging the cell in-circuit 2) connecting your NodeMCU to a USB port (since 5V will go to the ESP VCC, likely destroying your battery) Last but not least, it's outside of the datasheet specification (especially at 4V) and I personally wouldn't do it, unless it's a throwie.

Key characteristics:

• Max current: 1.4A
• Max voltage: 6.5V
• Dropout at 1A - 0.45V, at 0.4A - 0.1V
• Page 21 of datasheet, 1A rating taken from the 85C graph, 0.4A rating taken from the 25C graph (as temperature will increase with current).