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.

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    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. Apr 16, 2013 at 21:22
  • @MonicaCellio this is an official rule?
    – Yehoshua
    Apr 16, 2013 at 21:26
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    Here's the SE FAQ entry on drawing attention to old questions. Apr 16, 2013 at 21:34
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    Dina d'malchuta dina; it's SE's platform. :-) Apr 16, 2013 at 21:39
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    You can also check out the relevant portion of our local Mi Yodeya FAQ judaism.stackexchange.com/faq#bounty
    – Double AA
    Apr 17, 2013 at 2:39

2 Answers 2


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."

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    I also made a search and found this. But no reasoning is offered...
    – Yehoshua
    Feb 7, 2013 at 13:03
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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 7, 2013 at 18:55
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    I could have cited this dinonline.org/2011/08/16/… 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 7, 2013 at 19:18
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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 7, 2013 at 19:43
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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 7, 2013 at 20:50

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

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