ESP32 Forum

Supercapacitors have come a long way over the years, and recently some high capacity 3.8V supercapacitors have hit the market at very reasonable prices.

This is a 30F Eaton supercapacitor charged up to 3.3V powering an ESP32-S2 board completely — it can provide more than enough power for WiFi transmissions, with no power management or circuitry or code necessary! I was able to run the “restful_server” HTTP protocol example for a full 15 minutes!
I’m using one as a backup power supply to compensate for a puny LDO that can only output about 60mA, and it works like a charm!

Hi,

That's really cool! Super caps are so cool! I did something similar with 2x Maxwell 3000F 2.7V ultra caps!

3000F

3.8V supercapacitors are incredibly useful because you can charge them directly from a 3.3V power source, and discharge them at nearly 3.3V for a loooong time. Paired with an LDO with a very low voltage dropout such as the TLV75533, one could probably power an ESP32 in deep sleep indefinitely from a cheap 3V solar cell.

In practice, I’m using the supercapacitor to smooth current demands. The supercap has a low internal resistance from which I can siphon ~350mA worth of 3.3V power on demand without causing a big voltage drop on my primary 60mA power supply that would otherwise cause the ESP to reset. No additional circuitry is required, that’s just how supercapacitors work!

3.8V supercapacitors are incredibly useful because you can charge them directly from a 3.3V power source

Technically yes. But you should not do that. A supercap that is low will act like a dead short to any power supply for a long time until it gets near a full charge. So if your using a PS that cannot handle a dead short for a long time you will smoke it.
There are IC designed for using super caps that should be used. They prevent this, and charge the cap with a configurable current setting.