A shul keeps a defibrilator in a closet. While passing the closet on Shabbat, someone hears the machine beeping. He opens the closet, and sees a warning light saying "low battery".

The shul has many elderly people attending services Shabbat morning, and they have had frequent situations where they have needed to use the defibrillator on Shabbat. As this machine can save a person's life, the machine must be readily operative in an emergency.

May a person change the battery on the defib on Shabbat so that it will be available for a possible emergency that may or may not occur on Shabbat?

My question is not limited to a defib. It's just an example. It can be generalized to knowing of one may do melacha on any equipment so that it will be ready for a possible emergency? E.g. on Shabbat, can one change a dead battery on an ambulance?

  • A low battery is still working. I don't see what the Pikuach Nefesh here is.
    – Double AA
    Commented Jan 27, 2017 at 16:49
  • 4
    @DoubleAA The battery may be dead at the point that you have to use the defib. The essence of my question is if one is allowed to take precautions on Shabbat. Changing the battery at the time of the actual emergency may take too long to save the person's life.
    – DanF
    Commented Jan 27, 2017 at 16:51
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    FWIW, I asked this question to a neighborhood rav. I also mentioned the comparison of what happens with Hatzalah, as shown in the answer below. He mentioned that the Willamsburg Hatzalah has Gentiles who drive the ambulance back from the hospital to the Hatzalah dispatch, as they do not rely on R. Moshe's leniency that allows Jews to do it. Similarly, the rav suggested that a Gentile should change the battery on the defib, if this is possible. If no Gentile is available, he said MAYBE a Jew can do it, but he wasn't certain. Needs more research.
    – DanF
    Commented Jan 30, 2017 at 3:24
  • Regarding the defib., the rav I spoke to asked how long does it take to change the battery. I am unfamiliar with this to know the answer. Does anyone know? He said that if it's a few seconds, then, probably no one should change it until the pikuach nefesh situation arises.
    – DanF
    Commented Jan 31, 2017 at 17:49
  • judaism.stackexchange.com/q/87465/1739
    – robev
    Commented Mar 29, 2020 at 18:13

2 Answers 2


We have Hatzallah members in our shul and our rav (as well as Rav Heinemann of Baltimore) instructed them to drive whatever vehicles needed to be used for an emergency back to the central location after servicing the emergency. If necessary, they are also to maintain the supplies and equipment in the ambulances at the appropriate level. They are also to have their cells turned on (and not just set to vibrate) and kept with them all Shabbos (including in shul).

This would seem to be an equivalent case to what you ask. Of course, someone should be in charge of checking the equipment before Shabbos so it would not be necessary to plug it in on shabbos.

I do not have time before shabbos to find an online citation.

  • See my comment, above. Apparently, not everyone follows the viewpoint that you mentioned regarding the ambulances.
    – DanF
    Commented Jan 30, 2017 at 22:28
  • Since we are in Baltimore, Hatzallah follow Rav Henemann's psak. Each community must follow the psak of its rav. Commented Jan 31, 2017 at 0:34
  • R' Mantel at KAJ/WH holds the same way, as do most in NY, aside from Satmar, who employ non-Jewish drivers to avoid the issue Commented Mar 29, 2020 at 17:55

Disclaimer: Nothing on this site is intended to be used as an actual ruling in real life, but especially here where it could end up as a matter of life or death please do not take this as any sort of ruling.

Without getting into the details of what level violations would be involved in any given case, there is a responsum (Igrot Moshe Y.D. 3:155) from R. Moshe Feinstein that seems to address the underlying issue of doing something forbidden now in order to be able to help in a potential future case of pikuach nefesh. The question he was addressing was whether a kohen could attend medical school if he would have to be exposed to tum'at meit (which is forbidden for a kohen). Someone had apparently advanced the argument that the prohibition of becoming tamei should be overridden by pikuach nefesh, since, as a doctor, the kohen would be saving lives. R. Feinstein responded to this particular argument (he addressed several other points as well) as follows:

אבל מתיר מצד אחר דפקוח נפש וזהו שטות והבל שלא ניתן לבר דעת לומר כלל שאף אם לא היה שום רופא בעולם ליכא חיוב מצד פקוח נפשות ללמוד חכמת הרפואה דהחיוב דפקוח נפש איכא לכל אדם שיציל חברו במה שיכול שאם הוא רופא מחויב להציל חולה מחליו אבל ליכא חיוב שילמוד חכמת הרפואה כדי להציל חולה מחליו וכמו בצדקה שאם יש לו לאדם ממון מחויב ליתן צדקה אבל ליכא חיוב על האדם לעשות מסחרים ולהתעשר כדי ליתן צדקה

But he permits it from a different angle, that it is pikuach nefesh. And this is folly and nonsense that is not appropriate at all for someone with intelligence to say. For even if there was no doctor in the world there would be no obligation, on account of pikuach nefesh, to study medicine. This is because pikuach nefesh [means] that each person has to save his fellow in whatever way he can – if he is a doctor he is obligated to save an ill person from his illness. But there is no obligation to study medicine in order to save an ill person from his illness, just like by tzedakah where if someone has money he is obligated to give tzedakah, but there is no obligation on a person to engage in business [in order] to become wealthy in order to give tzedakah.

If we transfer this reasoning over to the case here, we should say that just like we don't have to study medicine (and therefore are not allowed to if it violates some other prohibition) because someone might later die that we could have saved had we studied medicine, we also don't have to maintain a working defibrillator (and therefore are not allowed to if it violates some other prohibition) because someone might later die that we could have saved had we had one.

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