Solar Powered Wrist-Watch on Shabbos

Question

Is one allowed to go out with a solar powered watch on Shabbos (where they know the watch is in a situation where they will surely benefit from the power produced through the sun?) What could be the possible issur or malachca in this (if any?)

For all practical situations a Rov should be consulted. I'm asking the question to find sources for this, authoritative poskim that discussed it or perhaps "svaras" that people have in order to answer this.

Yehoshua, please do not edit questions just to bump them; that's not what edits are for. To draw attention to older questions you can make a substantial edit (if it's an improvement :-) ), offer a bounty, mention it in chat, or circulate the URL outside of this site in hopes of drawing outsiders in who can answer it. Thanks. — Monica Cellio, Apr 16 '13 at 21:22
Here's the SE FAQ entry on drawing attention to old questions. — Monica Cellio, Apr 16 '13 at 21:34
@MonicaCellio Hmmm, I don't see anything in Halacha that says it's wrong for me to bump my questions. Adaraba! Torah hi v'limud ani tzrich! — Yehoshua, Apr 16 '13 at 21:37
You can also check out the relevant portion of our local Mi Yodeya FAQ http://judaism.stackexchange.com/faq#bounty — Double AA, Apr 17 '13 at 02:39

score 1 · Answer 1 · answered Feb 07 '13 at 12:40

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From http://www.science-halacha.com/elec/elec_eng_A1.htm

"A solar-powered watch is run by the current produced by a battery that is recharged by current produced through the exposure of the watch to light. If there is enough electrical energy stored in the battery to keep the watch moving all Sabbath then he is permitted to move it from a dark room to a lighted room. If there is not enough energy to keep it going all Sabbath, he may not move it from a dark room into a lighted room but he is permitted for the rest of Sabbath to remain with it in a lighted room since he is not doing an action to improve the functioning of the watch."

answered Feb 07 '13 at 12:40

rosends

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I also made a search and found this. But no reasoning is offered... – Yehoshua Feb 07 '13 at 13:03
the revach site has this line "but a solar cell generates electricity completely passively and would not involve any melacha on Shabbos. " – rosends Feb 07 '13 at 13:41
And what if the battery is about to finish and walking into the sun will allow it to continue. Is this still called "passive"? I also saw the Revach site and wasn't so impressed – Yehoshua Feb 07 '13 at 13:43
+1, decent answer by the answer-poster here: he cites his source and quotes just enough to answer the question. Disagreement with his source is not affecting my vote: readers can independently assess his source. Ping @Yehoshua. – msh210 Feb 07 '13 at 14:45
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@msh210, I'm not convinced that this answer is satisfactory for the question. It cites a source of no known value to me (or, I would posit, most readers), nor does it cite its own source or reasoning. If I create a website that's called "All Torah Here" and post my own innovative ideas about Halachah and Hashkafah, would that suffice as a "source" for answers to questions on MY? This could be fun... – Seth J Feb 07 '13 at 18:55
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I could have cited this http://www.dinonline.org/2011/08/16/wearing-a-self-winding-watch-on-shabbos/ and extrapolated that if a kinetic watch is ok then kal vachomer where no action is present the solar watch is ok. Or I could have let the revach site say the same thing because who am I to provide any interpretation? If the answer isn't CYLOR then it should be "this is what others have said to this question." and then CYLOR. – rosends Feb 07 '13 at 19:18
@Dan, that's a fair point (about CYLOR), but I think the point being asked is, what are we to make of this, and what issues are at play? The question is really, what has been written about this subject and by whom? If it's just some ideas from a random website, that would not be satisfactory to me. – Seth J Feb 07 '13 at 19:36
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unless that IS what has been written. And unless we have a whitelist of approved halchic sources, then I would think that an answer reports and a questioner then has to vet the authorities according to his particular hashkafah and standards. – rosends Feb 07 '13 at 19:43
@Dan I'm looking for mareh makomos or svaras. – Yehoshua Feb 07 '13 at 20:43
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@Yehoshua that's fair, but then I would think that the question wouldn't be worded looking for psak halacha ("Is one allowed") but would be worded looking for that logical process ("why would it be a problem...") – rosends Feb 07 '13 at 20:50
@SethJ AllTorahHere.com would be enough of a source to not downvote the poster, who doesn't necessarily need to evaluate the provenance of every source if it looks worthwhile to post. (Unless you know the data presented from the site or the presentaion of it is inaccurate.) – Double AA Feb 07 '13 at 22:20

score 0 · Answer 2 · answered Jul 02 '13 at 18:51

It is permitted to wear the watch, even though walking outside with it will cause the battery to charge, because one is walking regulary and is not doing any special direct action to cause the battery to charge. Please see following link for sources: https://docs.google.com/document/d/1EajOElJmCJ-fWnPyOy24ALdXIkBSY8Kp5TJ_MZzC8bw/edit?usp=sharing

Solar Powered Wrist-Watch on Shabbos

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