Suuuuuper simple circuit to wirelessly power an esp32-S2 dev kit with a supercapacitor

[lowtolerance]

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!

B65CC094-9979-414B-80F8-A3279305FF0A.jpeg (3.06 MiB) Viewed 12814 times

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!

[ESP_Minatel]

Hi,

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

[lowtolerance]

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!

[username]

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.