user69167: If I want to connect a LiFePO4 battery (as the power supply) directly to an esp32 - would this be the correct way: the plus of the battery to the 3.3 volt pin and the minus to a ground pin?

user4143: No. Absolutely not.
A LiFePO4 battery is 4.2V when fully charged. The absolute maximum voltage of an ESP32 is 3.6V.
You will kill the ESP32.
Instead you need to have a voltage regulator with a very low dropout. Ideally a switching ("buck") regulator with a zero-dropout "pass" mode to give the maximum life from your battery.
Even better is a "buck/boost" battery regulator that will boost the voltage up to a stable 3.3V once the battery voltage drops too low.
If all this is beyond you then you're better off using a powerbank to do the regulation to 5V for you then convert that back down to 3.3V with a simple buck regulator.

user82779: I know this question is two years old but it still pops up on research. I just wanted to add something from my experience with this:
If you take an Enerpower HTCFR18650 for example datasheet you see that the maximum voltage isn't 4.2V but 3.65V +/- 0.05V. While this technically is a little bit above the absolute maximum rating of the ESP32 (3.6V), in a non critical environment you can absolutely use the battery without voltage regulator. Just keep in mind that you also will not have any undervoltage protection in this case.
I'm not a fan of this negativity ("you will fry", "you kill you ESP", "Everyone will die"). An ESP32 costs $1. Just try it and if it works its great (it does) and if it doesn't, don't blame me ;)

69167: <p>If I want to connect a LiFePO4 battery (as the power supply) directly to an esp32 - would this be the correct way: the plus of the battery to the 3.3 volt pin and the minus to a ground pin?</p>
 4143: <p>No. Absolutely not.</p>
<p>A LiFePO4 battery is 4.2V when fully charged. The absolute maximum voltage of an ESP32 is 3.6V.</p>
<p>You <strong>will</strong> kill the ESP32.</p>
<p>Instead you need to have a voltage regulator with a very low dropout. Ideally a switching (&quot;buck&quot;) regulator with a zero-dropout &quot;pass&quot; mode to give the maximum life from your battery.</p>
<p>Even better is a &quot;buck/boost&quot; battery regulator that will boost the voltage up to a stable 3.3V once the battery voltage drops too low.</p>
<p>If all this is beyond you then you're better off using a powerbank to do the regulation to 5V for you then convert that back down to 3.3V with a simple buck regulator.</p>
 82779: <p>I know this question is two years old but it still pops up on research. I just wanted to add something from my experience with this:
If you take an Enerpower HTCFR18650 for example <a href="https://enerpower.de/wp/wp-content/uploads/2019/07/Technical-Specifications-HTCFR18650-1800mAh-3.2V-EN.pdf" rel="nofollow noreferrer">datasheet</a> you see that the maximum voltage isn't 4.2V but 3.65V +/- 0.05V. While this technically is a little bit above the absolute maximum rating of the ESP32 (3.6V), in a non critical environment you can absolutely use the battery without voltage regulator. Just keep in mind that you also will not have any undervoltage protection in this case.</p>
<p>I'm not a fan of this negativity (&quot;<strong>you will fry</strong>&quot;, &quot;<em>you kill you ESP</em>&quot;, &quot;<em><strong>Everyone will die</strong></em>&quot;). An ESP32 costs $1. Just try it and if it works its great (it does) and if it doesn't, don't blame me ;)</p>
