Comment by logicallee | Hacker News Reader

Comment by logicallee | Hacker News Reader

meanwhile the latest and greatest 2015 device is an all-day wristwatch the weight of a pack of cards [1] (for the smaller Apple watch [2]) that in Apple's own "watch test" tells time for up to 48 days before dying --- whoops, no, I meant 48 hours [3] :

>Testing conducted by Apple in March 2015 using preproduction Apple Watch and software paired with an iPhone using preproduction software with 5 time checks (4 seconds each) per hour.

This is as compared with simple mechanical wristwatches that are self-charging (through wrist movement) and can be worn indefinitely, or have 72-100 hour power reserves from winding. [4] This is mechanical power we're talking about.

So don't talk to me about decades until you can get more than 48 hours of battery life....from a watch.

1 http://en.wikipedia.org/wiki/Standard_52-card_deck

2 https://www.apple.com/watch/apple-watch-edition/18-karat-yel...

3 https://www.apple.com/watch/battery.html

4 http://forum.tz-uk.com/showthread.php?250883-List-of-watches...

The Pebble has much better battery life than the Apple Watch; it can last for a week on a 130 mAh battery. To achieve that, the Pebble uses a microcontroller with 512K of flash (plus 4 MB of flash on a separate chip) and 128K of RAM. Presumably the Apple Watch uses a higher-end application processor and DRAM.

Sure, the Apple watch is fairly likely to be a ridiculous geegaw.

It's also going to do a lot more than the mechanical watches you are comparing it to.

If you just want to tell time, there is a wide market of solar watches:

http://www.casio-intl.com/asia-mea/en/wat/standard/solar_pow...

http://www.seiko-cleanenergy.com/watches/solar/

The Seiko tech runs for 6 months with no charging (left in total darkness).

I wonder what the actually numbers for these watches are. Energy received via the solar cell, energy consumption, battery capacity.

Some bookending it is as least possible. They imply that the draw is no more than 1/60th the input (1 minute of sun for 1 hour). The 3 hours for 6 months would be much lower, checking their documentation, it enters a low power mode that freezes the hands (it still keeps time, the hands are advanced when power becomes available).

The input is limited to something like 10 square cm (that's a bit more than 3 cm by 3cm, or a circle ~3.5 cm across). 1000 watts / square meter is usually used as peak sun, so the max input would be ~1 watt (but actual energy captured would probably be more like 1/10 of that).

3 Watt hours is a very respectable figure for a AA battery, so it clearly isn't storing that much power. After looking up that figure, 10% efficiency for the solar cell is probably high.

Yup, I've had a Citizen eco-drive (solar powered watch) which has been going 10+ years.

It's an interesting model - there's some form of drive mechanism for the analog hands that let them move independently of the time. I.e. if you turn it to stopwatch mode, the hands will move to 12:00 and use the minute hand for marking minutes.

I've always wondered what kind of electronics are in there - and if they're even digital.

This reminds me of the people who, at the dawn of the smartphone age, were proudly boasting of their dumbphone's week-long battery life vs. the nightly recharging required by smartphones.

Until they realized they were completely missing the point, since they were comparing a phone to _a pocket computer with a constant data connection_. Most have since stopped boasting and just silently plug in their phone every night.

Pebble lasts a week

Reply on news.ycombinator.com