I have a ESP32 (38 pins) that I want to feed (if possible) with 4 AA batteries.
I was reading a lot of info that there is a lot of difference if you use Alkaline or NiMH. Honestly I didn't know they behave so differently. First of all I will try with NiMH, but I would like to be flexible in case some day I want to use Alkaline.
Also read that I would need a boost/buck converter to 3.3 in my particular case. With that it would be sufficient? I don't want to fry the device :P.
And my last question, where in the board should I connect the 3.3 input? in the 3.3 pin? currently I'm using it to feed my sensors. Ideally I would use the USB port for that matter, but I believe it would make things more complicated.
Hello,
in addition to other battery characteristics,
in your case, what matters most are the voltage and current they can supply.
The current will determine "how long" you can use the battery.
Remembering that Alkalines are not rechargeable and NiMH are rechargeable.
The Alkalines are 1.5V each, and using 4 in series you will have 6V,
the NiMH are 1.25V each, and using 4 in series you will have 5V.
NiMH Batteries can supply more current than Alkalines batteries. See the graph.
Regarding your doubt:
If you were going to use only NiMH batteries, I would say you could power it via the +5V Vin pin on your ESP.
But how do you want to have the possibility of also feeding with Alkaline batteries, you should really use a boost/buck, and feed via the 3.3V pin.
But be very careful, as the 5V or 3.3V pins do not have internal polarity inversion protection, and if you feed them inverted + with Gnd, you could completely damage your ESP.
If you have some knowledge of electronics, see the schematic:
Note from the graph shown that Alkaline batteries are down to under 1.2V half way through thier capacity, and only provide a higher voltage than NiMh for about 30% of their capacity.
