3 ms·

How much time can you get off a lipo pouch? If it's "on the wall", why isn't it powered by an ac adapter?

sho_hn 4y ago
> How much time can you get off a lipo pouch? Time will tell, but I'm hoping for at least a couple of months on a 1100 mAh. Napkin calculations had me at 6-7 months. It's e-ink, so I can shut down the entire display and controller after the refresh, and the ESP32 is in deep sleep until it wakes up on timer and performs a network fetch and display update, then back to sleep. > If it's "on the wall", why isn't it powered by an ac adapter? Effort :-) It's a picture frame on a wall, I don't want to have an externally visible cable going into it and burying a cable in the wall is more work than all the rest of it.
- knodi123 4y ago
  Wow, I'm not used to thinking of batteries in those terms. If you hit 3 months, you deserve to crack a bottle of champagne, that's a really impressive bit of engineering. Although now that I think about it, smoke detectors have been lasting a year on a 9-volt for all my life, so maybe I'm just short-sighted. :-)
  - sho_hn 4y ago
    An ESP32 just draws about 0.15mA or less in deep sleep mode, even less if the ULP co-processor is turned off - down to about 5 µA if you're willing to keep no state/data around and just need timer wakeup. That's 220000 hours of hibernation on an ideal 1100 mAh battery (i.e. one that doesn't lose charge by itself over time)! In practice this is unattainable, because batteries are not ideal, and there's quite some efficiency loss from e.g. voltage regulators. But you can realistically get to years of hibernation. Of course the power draw is much higher if you e.g. need to permanently keep a WiFi connection open and can't sleep (there's lower-power alternatives to WiFi like ESP-NOW for some applications), but I just need a connection for a very short time to fetch a 1600x1200x4 image. And to power a full display refresh on the e-ink panel. If you think about it, a Kindle or similar also runs for days to weeks off a single charge, and that has a lot more interaction and computation going on during use, a more powerful processor with higher power draw and it sleeps less deeply and for shorter time. My application is suitable to extend beyond that by a large factor.

> How much time can you get off a lipo pouch? Time will tell, but I'm hoping for at least a couple of months on a 1100 mAh. Napkin calculations had me at 6-7 months. It's e-ink, so I can shut down the entire display and controller after the refresh, and the ESP32 is in deep sleep until it wakes up on timer and performs a network fetch and display update, then back to sleep. > If it's "on the wall", why isn't it powered by an ac adapter? Effort :-) It's a picture frame on a wall, I don't want to have an externally visible cable going into it and burying a cable in the wall is more work than all the rest of it.

knodi123 4y ago
Wow, I'm not used to thinking of batteries in those terms. If you hit 3 months, you deserve to crack a bottle of champagne, that's a really impressive bit of engineering. Although now that I think about it, smoke detectors have been lasting a year on a 9-volt for all my life, so maybe I'm just short-sighted. :-)
- sho_hn 4y ago
  An ESP32 just draws about 0.15mA or less in deep sleep mode, even less if the ULP co-processor is turned off - down to about 5 µA if you're willing to keep no state/data around and just need timer wakeup. That's 220000 hours of hibernation on an ideal 1100 mAh battery (i.e. one that doesn't lose charge by itself over time)! In practice this is unattainable, because batteries are not ideal, and there's quite some efficiency loss from e.g. voltage regulators. But you can realistically get to years of hibernation. Of course the power draw is much higher if you e.g. need to permanently keep a WiFi connection open and can't sleep (there's lower-power alternatives to WiFi like ESP-NOW for some applications), but I just need a connection for a very short time to fetch a 1600x1200x4 image. And to power a full display refresh on the e-ink panel. If you think about it, a Kindle or similar also runs for days to weeks off a single charge, and that has a lot more interaction and computation going on during use, a more powerful processor with higher power draw and it sleeps less deeply and for shorter time. My application is suitable to extend beyond that by a large factor.