user49195: I'm trying to connect a ~5.5V (2 x 3V coin cells in series, but their voltage drops a little) to the VBat (or V+) of my Adafruit Huzzah ESP8266 module (not the black Feather one, the smaller blue one: https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/pinouts)
Whenever I do that the voltage output from the 3.3V pin drops to ~0-1 V and thus the ESP stops working.
However when I use the FTDI cable (3.3 V) and connect it to my laptop, there is no problem, I get almost 3 V.
I also added a 1000mF capacitor to smooth out voltage signals and actually that also helps to increase the volt a little (without it I get almost a 0 V on the 3.3V output)
Any ideas? 

user49195: After tinkering more, I figured out that the Huzzah module is happy to take in up 4.5V via a 3 AAA battery cell so I guess it's ok up to 5V since my previous battery input was over 5V.
That's a little weird considering that in Adafruit's page, it says 

..to make it easier to power, we put a high-current-capable 3.3V
  voltage regulator on the board. It can take 3.4-6V in but you should
  stick to 4-6V since the ESP8288 has high current usage when WiFi is
  on.

Hope this may help someone else.

49195: <p>I'm trying to connect a ~5.5V (2 x 3V coin cells in series, but their voltage drops a little) to the VBat (or V+) of my <strong>Adafruit Huzzah ESP8266</strong> module (<strong>not</strong> the black Feather one, the smaller blue one: <a href="https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/pinouts" rel="nofollow noreferrer">https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/pinouts</a>)
Whenever I do that the voltage output from the 3.3V pin drops to <strong>~0-1 V</strong> and thus the ESP stops working.</p>

<p>However when I use the FTDI cable (3.3 V) and connect it to my laptop, there is no problem, I get almost 3 V.</p>

<p>I also added a 1000mF capacitor to smooth out voltage signals and actually that also helps to increase the volt a little (without it I get almost a 0 V on the 3.3V output)</p>

<p>Any ideas? </p>
 49195: <p>After tinkering more, I figured out that the Huzzah module is happy to take in up <strong>4.5V</strong> via a 3 AAA battery cell so I guess it's ok up to 5V since my previous battery input was <strong>over 5V</strong>.</p>

<p>That's a little weird considering that in Adafruit's page, it says </p>

<blockquote>
  <p>..to make it easier to power, we put a high-current-capable 3.3V
  voltage regulator on the board. It can take 3.4-6V in but you should
  stick to 4-6V since the ESP8288 has high current usage when WiFi is
  on.</p>
</blockquote>

<p>Hope this may help someone else.</p>
