There are now many electronic watches on the market that contain rechargeable batteries that are charged when the face of the watch is exposed to light, in particular the Citizen Eco-Drive watches. When fully charged, these watches have enough power to run for several months. Is it permissible to wear such a watch on Shabbat? There are also electronic watches that are recharged by movement of the wrist, in particular the Seiko Kinetic watches. Can these be treated similarly to automatic mechanical watches and be worn on Shabbat?
Yes, since the watch is working anyhow, the person is not doing a “ma’aseh”, an action which turns it on. There is no problem by extending the amount of time that the watch is going to work as long as it is working now, like extending a “Shabbis clock”. It is not considered “Mitakem Manah”, fixing a tool. The same goes for the watches that are recharged by movement. Rabbi Dov Li'or