Can we run the ESP32 on 2x AA batteries

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kolban
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Can we run the ESP32 on 2x AA batteries

Postby kolban » Sun Aug 20, 2017 5:19 am

Howdy folks,
My electronics skills are poor and this may be a silly question....

Can we run an ESP32 on two AA batteries?

What is giving me pause is that I think the ESP32 needs 3.3V while if an AA battery is only 1.5V then 2x would be 3.0V and not 3.3V.

Obviously there may be other reasons beyond the above that would prevent me running an ESP32 on AA's and I'm all ears to hear.

Neil
Free book on ESP32 available here: https://leanpub.com/kolban-ESP32

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loboris
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Re: Can we run the ESP32 on 2x AA batteries

Postby loboris » Sun Aug 20, 2017 8:25 am

The voltage of the alkaline battery at 50% capacity is only 1.3V so it can hardly be used for powering ESP32.
You could use DC DC Boost Converter (step-up) like this one to get 3.3V from two alkaline batteries. It has high efficiency and low quiescent current and can use the full capacity of the battery.

The only battery type which could power the ESP32 directly is lithium iron phosphate (LiFePO4) battery which has flat discharge curve at ~3.2V. It is also available in AA package.

Image
I've just ordered one for testing,

ESP_Sprite
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Re: Can we run the ESP32 on 2x AA batteries

Postby ESP_Sprite » Mon Aug 21, 2017 12:27 am

This is entirely unofficial and you shouldn't make a commercial product on this, but I think in practice it would work mostly OK. The ESP32 can actually handle a fairly large range of power supply voltages (down to 2V or so, if memory serves), it's usually the flash that craps out, and that happens when the voltage gets around 2.5V. (Most of them are specced to 2.7V, but they'll run on a bit less as well.) That should allow a module to work to at least 50% of their capacity; not the longest life there is, but still OK. The catch is that I have no idea how the internal resistance of the battery react to the peak-ish power draw that WiFi has: it may be that that lets the voltage drop too much and have the entire thing crap out. You may be able to solve that by connecting a beefy (2200uF or so) low-ESR in parallel over the batteries. Alternatively, grab a module somewhere that uses 1.8V flash, it should be able to work on a lower power supply as well.

Baoshi
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Re: Can we run the ESP32 on 2x AA batteries

Postby Baoshi » Wed Oct 18, 2017 12:59 am

I’m evaluating PICO-D4 vs D2WD in a 2xAAA project.
In this sense, PICO with bounded GD25 flash (3.3v) is not as good as D2WD with internal 1.8V flash? Although both devices are rated at 2.3-3.6V ?

WiFive
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Re: Can we run the ESP32 on 2x AA batteries

Postby WiFive » Wed Oct 18, 2017 2:37 am

Gd25 3v flash only rated down to 2.7v? So yes it seems 2.3v is not relevant spec.

Baoshi
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Re: Can we run the ESP32 on 2x AA batteries

Postby Baoshi » Wed Oct 18, 2017 4:54 am

WiFive wrote:Gd25 3v flash only rated down to 2.7v? So yes it seems 2.3v is not relevant spec.

I think this way too. Seems the datasheet needs update

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