Notices by joey castillo (joeycastillo@mastodon.social)

@josecastillo Battery test, day 380: 2.59 volts. To reiterate the parameters of the test: this watch (red line on the graph) is running an old firmware from 2021 that lacks some low power optimizations I did early this year. I also started a new watch (green line) in February of this year that I've been wearing daily since; it's still sitting pretty at 3.08 volts here on day 275.

I'm going to post a Sensor Watch battery update later today, and this post is to connect it to the old battery test thread. If you're new to this: in late 2021, I put a fresh coin cell into Sensor Watch, my board swap for the Casio F-91W wristwatch. This month that watch hit one year on that same battery, and in this thread I'm tracking how long the battery will last. You can click the “Replying to @josecastillo” link repeatedly to get back to the beginning of the test. https://twitter.joeycastillo.com/josecastillo/status/1590059216798388224/

@josecastillo Battery test, day 400: 2.4 volts. It’s low enough now that the extra power of beeping the buzzer on mode change causes a voltage drop to ~2.3, but it recovers to 2.4 over about ten seconds. New firmware is back up to 3.08 volts here on day 295! Both lines are red this time, but it’s the one on top.

@josecastillo Forgot to post this yesterday! Battery test, day 390: 2.51 volts. I think we're finally near the end with the old firmware; I expect it'll die within a week or two. There's an app note that once the LCD voltage is more than 700 mV above the system voltage, current consumption increases, and I think I can see that on the red line: it's dropping faster now that we've crossed the threshold. New, more efficient firmware though: still going strong! 3.07 volts at day 285.

BATTERY TEST, DAY 425: THE END. I measured 1.8 volts two days ago, which officially marks the end of the graph’s Y-axis. Today I woke it up for this test and watched it sag from 1.7 to 1.4 volts as I changed modes, the LCD dimming slightly in between each button press. Then I caught the exact moment this test ended: 11:46 AM central time, or 10,198 hours continuously running the old firmware. 🫡

Battery test, day 420 (and 315): 1.97 and 3.07 volts. Might be the last time these two get photographed together. I also brought them both into the backcountry, where they hung on a branch for one last night of temperature logging. It’s wild that running on this same coin cell, that gray watch logged temperatures in Big Bend in December of 2021. Even with the old firmware, this watch ran continuously for all of 2022, and saw three calendar years. And at just shy of 2 volts, it’s still going…

@josecastillo Battery test, day 410: 2.195 volts. (Mostly 2.19, but it did hit 2.20 once). No more big voltage drop when I press the mode button, which signals to me that its steady state current consumption is higher now. That and the steepening of the red line 😬. This microcontroller operates down to 1.62 volts, which gives me optimism that this watch with the old firmware will still be with me in 2023, if only for a few days. (New firmware, green line: 3.07 volts at day 305.)

Also just to give a sense of perspective: the graph I keep posting is the manufacturer's data sheet scaled by a factor of ten. In an apples-to-apples comparison, you can see where the blue line, the manufacturer's simulation, dies at 1000 hours; how the Sensor Watch with November 2021 firmware outlasts it to run for over a year; and how the February 2022 firmware outlasts even that test. With improved crystal and cap selection, the new hardware revision could outlast even this one. Wild stuff!

NEW battery test, day 330: 3.07 volts. While the 2021 watch is dead, the stainless steel watch running the February 2022 firmware keeps running strong. In just over one month’s time it’ll hit the one year mark, and still today it sits at nominal voltage. Bold prediction: I’ll still have this very watch, powered by this same coin cell, on my wrist come January 2024.

Napkin math suggests that if we accept the rated capacity of 100 mAh and divide that by the 10,198 hours of runtime we achieved, we’d get an average current consumption of 9.806 microamperes — which tracks astonishingly close to the hypothesis I posted at the outset, fourteen months ago.

New battery test, day 365: 3.08 volts. One year on the wrist and we’re still at nominal voltage! This signals strongly, to me, that we aren’t yet at the halfway point of this test, and that as configured and shipped to backers, Sensor Watch may in fact have TWO-year battery life. Anyway I’m going to science about it for the rest of 2023; we have fucked around with the firmware, and now we find out what happens. Isn't that what the scientific method is all about?

Quick followup on day 354: it's been at 3.07 volts ever since, and I realized: in the days leading up to day 350, I'd been wearing a different watch to test some firmware changes. As a result, the steel watch had been sitting at room temperature for about a week — not warmed up to 90° F by my wrist. Lower temperature, lower voltage? Anyway it'll be a few weeks to months before I'm sure, but I think we're still at the top of the discharge curve; I don't think it's started curving just yet.

NEW battery test, day 350: 3.06 volts. The one year mark approaches! Also: I caught up with my friend Ben on day 348; he's been wearing a green watch that started its life on the same day. One difference: he left the hourly chime on, and his battery is at 2.94 volts over this same period. THIS IS A GREAT DATA POINT! It tells me that year-long battery life still holds with the chime turned on, and it's still more efficient than the old firmware (which was at 2.8 volts at this point in the test).

New battery test, day 450: 3.05 volts. Actually I'm calling it 3.045, because it was 3.04 when I arrived at the voltage measurement screen, and then it bounced right back. These latest numbers signal to me that we are, in fact, making the turn: the green line is beginning to curve ever *ever* so slightly downward, akin to what the old test — red line, with the less efficient firmware — did at day 200. Does this mean we're at the halfway point of this new test? Time will tell!

New battery test, day 425: 3.06 volts. This is a milestone. Day 425 was the day that the old watch with the old firmware — red line in the graph — finally went kaput. With the new, more efficient firmware (green line), the test watch remains at nominal voltage, one year and two months into the test.

New battery test, day 400: 3.07 volts. This is very exciting! It wasn't that long ago that the original battery test (red line) was limping over the 400 day mark at just 2.4 volts, the energy of beeping the buzzer causing it to drop 100 mV. With the new firmware, we're still sitting strong at nominal voltage, and even the heavy lift of lighting the green LED causes a drop of just 10 mV. 💪

New battery test, day 600: 2.91 volts. It’s settled: this watch, with its CR2016 coin cell installed in February 2022, will tick its way through a second trip to Pasadena for another visit to Supercon. Haven’t checked in with my buddy Ben, wearing the yellow line watch (with higher consumption due to the hourly beep); he’s abroad through mid November, and I’m wondering if it’ll still be running when he gets back. 🤞🏽

New battery test, day 550: 2.95 volts. We (green line) are in the turn, but I still expect this CR2016 coin cell to propel Sensor Watch from February 2022 to February 2024 at least. (I also caught up with my friend Ben, who started on the same day but kept his hourly chime enabled. As of day 244, his watch is riding the lower yellow curve, but it’s still solidly in the territory of “year-plus battery life.”)

New battery test, day 500: 3 volts. First (red) test fell off the Y-axis by dying; this one breaks the X-axis by surviving.
Also! This milestone happened while hiking the Lost Coast with my buddy Ben. A year ago February, before our big trek in Big Bend, I gave him a watch too. Main difference is he kept his hourly chime on for over a year. With 4 data points from him, I can project (yellow line) the impact of that: I sense his watch will make it to fall, while mine might make it through winter.

New battery test, day 675: 2.85 volts. Number hold steady! Tho I admit I've been on and off with this watch the last few weeks; I've been splitting my time between Sensor Watch and a stock Casio W800H, just to get a feel for a larger watch on my wrist. Anyway, onward to 2024!