AAA's and Boost Regulator for ESP8266 Project

Hi there,

So I’m looking to use 2x 1.5V Alkaline AAA batteries to power an ESP8266 project using the ESP-12 module and because of this battery constraint I’m looking to use a boost regulator, namely this one.

Here are some questions I have:

  • First of all, is this a good choice for such an application? The ESP-12 draws about 75mA with WiFi on, so it seems like this boost reg can handle that

  • Also, this particular boost reg seems to have a lower quiescent current (19uA) than other chips I found and at a reasonable price. However, am I looking at the right number in the spec sheet? For example, if the enable pin on the reg is always pulled high, and if the ESP-12 is normally in deep sleep (drawing like 60uA), what current will the boost reg draw?

  • The 1.5V batteries are usually about 1.65V when brand new, so that means 3.3V or even slightly more for 2x of them. However, for the boost reg to work Vin < Vout so if I set Vout = 3.3V, what happens if Vin is, say, 3.35V? Will the output just be 3.35V or will it cease to function altogether?

  • I’m trying to minimize the deep sleep current of the ESP, and I read here that it’s dependent on the operating voltage and is lower for lower voltages, so I’m trying to keep the voltage as low as possible while still having it operate reliably. The ESP8266 the spec sheet says it operates from 2.5V - 3.6V so would it make the battery life longer if I use a single AAA battery with a boost regulator set at 2.6V? Also, if I wanted to use 2x AAA’s, wouldn’t that be an issue if I wanted to set the output voltage to 2.6V since the battery voltage would start off at around 3.3V then drop down to maybe 2V? Would it be better for me to put then in parallel instead of series?

Thanks!

On page 10 of one of the data sheets you linked to you can find a reference schematic on how to produce 3.3V from a single 1.5V battery. Do note that this chip is just part of the circuit, and the power that comes out of it may be too noisy for the ESP to work with reliably. Try adding bigger caps to smooth it out.

When transmitting on WiFi the ESP may draw a lot of power, like 300-500 mA. This is for short boosts of course but your power supply must be able to handle this.

There are lots of tutorials out there about running the ESP8266 on battery power, and also how to use its power saving options.

Well I guess someone might know all the answers for that particular regulator.

Perhaps the first thing to do however is identify what the maximum current of the project is going to be, you cannot select a converter until you do .............

Are you planning to run this for some time? If so, forget it. Two AAA's will be drained by a ESP8266 in notime if the WiFi is on.

androidfanboy:
So I'm looking to use 2x 1.5V Alkaline AAA batteries to power an ESP8266 project using the ESP-12 module and because of this battery constraint I'm looking to use a boost regulator,

Won't it work directly from the 2xAAA batteries?

...R

Batteries can last a long time if the esp spends most of its time in deep sleep, which sounds like the OP's intention.

I run some of my Wemos Mini based sensors with a single 10440 size (= AAA) Li-ion battery. At full charge, these batteries output 4.2V, which is too high for the esp module (although some people do it anyway and report no problems). But the Wemos has a low-dropout 3.3V regulator, so I use that. This will waste some of the battery's energy, but they still last around 21 days. My sensors sleep for 15 mins, then wake and transmit their readings in 5~6 secs.

androidfanboy:
Hi there,

So I'm looking to use 2x 1.5V Alkaline AAA batteries to power an ESP8266 project using the ESP-12 module and because of this battery constraint

Very often there is an assumption that a boost converter is the way to go in low power applications since it allows you to reduce the number of batteries, a single AAA or AA for instance.

Do you have a compelling reason for wanting to power the circuit with 2 x AAA rather than 3 x AAA ?

3 x AAA is very much easier to implement and could actually be more power efficient, if this is Alkaline you are using (you did not say !) then they spend around 50% of their life below 1.3V.

I would be using Alkaline (I did mention this in the first sentence actually), but could use other types if needed. The main reason I'm wanting to use 1 or 2 is because I want this to be super compact and weigh less. As a disclaimer, I'm not a complete noob at electronics so there's a reason for some things I'm asking about, and I do understand that going from higher to lower voltage is more efficient but I'd like to know specifically how I would either use 1 or 2 AAA's. Actually I'm looking to use AAAA's, but I said AAA so I wouldn't confuse anyone. I'd also like to know if I can use the ESP at a lower operating voltage lile 2.6V to get longer battery life.

Thanks!

No, I don't think so. My esp give up at around 2.8~3.0V. The regulator on my Wemos drops around 0.2V, so 2.6V is right on the edge.

The spec sheet for the ESP8266 says it can work on 2.5 - 3.6V, so I'm assuming that it should work at the lower end of that voltage range as well. My guess is that the Wemos has an on-board 3.3V voltage regulator so it doesn't work at lower voltages, which makes sense, but as far as the ESP8266 itself, couldn't it operate at 2.6V?

So just to give a recap of my main question, since I haven't really had any direct answers so far:

  • Can I run an ESP-12 module on a lower voltage, say 2.6V. Datasheet says 2.5 - 3.6V. Again, I'm talking the ESP-12 module by itself, not using 3rd party dev boards that have on-board LDO's.

  • If I can run it at 2.6V, will programming at 3.3V be an issue? Can I just use a 1N4148 pointing away from the ESP's RX pin to the RX_3.3V programming pin?

  • Can I use a single AAA battery and use the boost regulator I linked with Vout = 2.6V? Specifically, will it be able to handle the max current drawn from the ESP-12 during WiFi transmission? If not, any suggestions on what boost reg to use that would have low quiescent current? I'm also assuming that if I can use a single AAA battery and boost it up, then I can use any number of the same AAA's in parallel for larger capacity but same voltage.

Thanks!

  1. Why doubt the datasheet?

  2. If you program it, won’t you just connect the 3,3V to Vcc as well (and disconnect the battery)? Otherwise I would simply add a resistor inline with the RX of the ESP to clamp the voltage.

  3. Why boost it right up to the edge then? You don’t give yourself an awful lot of headroom with 2,6V.

And two notes:

  • A ESP (or any WiFi device) is a pretty poor choice for small, long battery life…
  • I would say size wise you’re better of with a small LiPo. For the same energy as a single Alkaline AAAA you just need a ±150mAh pack

androidfanboy:

  • Can I run an ESP-12 module on a lower voltage, say 2.6V. Datasheet says 2.5 - 3.6V. Again, I'm talking the ESP-12 module by itself, not using 3rd party dev boards that have on-board LDO's.

I haven't taken my ESP8266's out of their wrapper yet. However I have several nRF24L01+ modules coupled to Atmega 328 running directly off a pair of AA alkaline cells.

I have had no problem programming the Atmega328s with a USB TTL cable (which may have 5v on its data pins) while the Atmega 328 and the nRF24 are powered from the battery.

...R

Any solution that avoids using the boost converter is the best.
Boost converters arnt very efficient at very low power levels, and short of turning the boost converter off when you dont need it , it will end up using more power than what its powering.

Well, there's no way around it with a AAA battery. Also, as long as Vin isn't that far from Vout it can be > 90% efficient. The Amazon dash button uses a boost reg.

androidfanboy:
The spec sheet for the ESP8266 says it can work on 2.5 - 3.6V, so I’m assuming that it should work at the lower end of that voltage range as well. My guess is that the Wemos has an on-board 3.3V voltage regulator so it doesn’t work at lower voltages, which makes sense, but as far as the ESP8266 itself, couldn’t it operate at 2.6V?

Why just assume and guess ?

How long would it take to check it out for yourself ?

androidfanboy:
Actually I’m looking to use AAAA’s, but I said AAA so I wouldn’t confuse anyone.

Thats a significant omission really.

If your intending to use AAAAs, you really do need to know how much current your circuit actually takes in practice.

Small alkalines are not very good for supplying large currents, so the voltage of the battery might dip under peak load, which increases the boost current, which drops the battery voltage etc …

androidfanboy:
Well, there's no way around it with a AAA battery.

Why?

And note that the OP said 2 x AAA cells

...R

First of all, I was hoping someone would happen to already know based on experience if the ESP runs on lower voltages. I can test it but would have to buy a standalone ESP module and solder wires to it just to see.

As far as there being no way around using a boost reg with 1-2 AAA's, how is that statement wrong? I can't just use 2 batteries in series because their voltage will drop below 2.5V eventually, and especially for battery measurement purposes I need a constant supply to the ESP otherwise ADC reference will be always different.

androidfanboy:
would have to buy a standalone ESP module and solder wires to it just to see.

Sorry. I thought that's what you were using.

And I got mixed up as to who was the OP.

...R