[Avodah] running creates electricity

[Akiva Miller via Avodah]

R' Micha Berger wrote:

> Assuming one can buy a garment that doesn't have an assur device,
> and is only used to charge a battery that isn't used until after
> Shabbos. If the charging is mutar, then the clothing is a keli
> shemelakhto leheter, and why would it be muqtzah?

In your example, I would think that the battery charger would be an example
of an "assur device". I would imagine that a discernible amount of heat is
generated in this process. And even you can find a way to say that no
melacha happens when the battery is charging, it is still hachana -
preparation for after Shabbos.

If one has some sort of device that uses this battery, and the device can
be used on Shabbos, then you've avoided this problem of hachana, but you've
introduced a different problem, that of repairing. In other words, charging
such a device is at least as problematic as winding a mechanical watch that
has stopped.

On the other hand, if I remember correctly, there's a difference between a
watch that has run down and stopped (which is now considered broken, and
winding it would be a forbidden repair), and wind-up spring-powered toys.
The normal use of such toys is to wind them up, play for a while, and the
spring runs down; because this is the normal pattern, the powered-down
spring is not considered broken, and so winding it on Shabbos is not a
forbidden repair.

If the device you're powering with this shirt is similar to a watch, then
you've got problems. But if it is more like the toys, then maybe there's a
slim chance that the shirt might be okay for Shabbos power.

Akiva Miller
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