How to charge a seiko solar watch

Seiko documentation for the movement and watch (an SNE039 in this case) warns about the movenment being damaged from the heat of direct sun charging. I have a window next to my desk with good sunlight in the afternoon. I try to put watch there when I'm working, but I've started to notice the case getting really hot to the touch after about an hour. Has anyone had a movement failure or poor timekeeping after a hot watch charge? It seems that sunlight is the most efficient way to charge these movements, but it may damage the watch. I'm thinking now to move the watch out of the direct light and bounce the sunlight off of a greeting card to the dial. Seems silly though.

Don't sit the watch by itself in direct sunlight. It will heat up. Possibly reaching about 120°f.

You see, when the watch is on your arm. Your skin acts as a heat sink. Blood flow will remove the extra heat.

Measuring the current temperature of the watch case I'm wearing. It's currently 90.8°f. My skin measures 91.4°f. If I were to take the watch off. It's temp would equalize with the surrounding environment. If in direct sunlight, expect temps above 100°.

This is also the reason a wedding band or necklace doesn't burn you as you're standing in the sun.

Leave it on a desk BY the window with the dial pointed at the window. Just make sure the sun does not impact it directly for any real length of time (more than an hour) and it will be fine.

Thanks for the replies. I tried moving it farther from the window but still in direct sunlight. That seemed to help keep the case from getting too hot. The placement is not ideal for my space, but good to know. Grasshopper, thanks for the tip. I may try putting the watch on a watch pillow to act as a heat sink the next time I charge it.

I hope creating a more robust solar movement is in the works for Seiko.

You could put it in a glass jar filled with water

Don't say that because someone will drink it.

Think coat hanger and a fish tank.

Can't speak for Seiko but my solar G-shock does heat up significantly while charging. As the watch is 20atm water resistant, I put it in a jar of water to cool it down.

Overheating the battery will eventually shorten it's lifespan and ability to recycle or charge.

I had Citizen solar's for over 15 years, always charged them by sitting on my desk with indirect sunlight and never had an overheating issue. My Seiko SNE437 that I only wear when working out sits in a watch box with glass cover under a window 75% of the time and seems to get plenty of light to keep it charged without overheating.

I had Citizen solar's for over 15 years, always charged them by sitting on my desk with indirect sunlight and never had an overheating issue. My Seiko SNE437 that I only wear when working out sits in a watch box with glass cover under a window 75% of the time and seems to get plenty of light to keep it charged without overheating.

Yeah, you don't need direct sunlight. Just leave it pointing at a window and don't wear it for a week. Once it's fully charged, just keep it somewhere with light and wear it in good health.

My Seiko Solar Chronograph (SSC017) has been running continually for years now and it's only reached the 2-second low power indicator once about a year ago. I put it near the window for a few days and it's currently still running. It's a bit slower than it used to be as it's now 1min, 30 seconds slow since I zeroed it out when DST started. By the time we go back to standard time it used to be no more than a minute off I think. My Kinetic GMT Diver is only 42 seconds fast so it's keeping better time.

Just keep them in regular light and they stay charged. Put it near a window when it's low (2-second indicator) and it should be fine.

I tried direct sun charging today with the watch around a white faux leather pillow. It seemed cool to the touch whenever I checked it, but the sun was going in and out of the clouds. I think the best idea is to just leave it near the window out of direct sun when it's not worn in rotation. I guess this would work for a Tank Solar as well.

Depends where you live as well. My solars live on a windowsill but here in Yorkshire they couldn’t overheat in full sun if they wanted to. If you find your watch getting a bit warm move it further into the room. It will still get plenty of light but less heat.

Are you charging it this way to bring it back from from low power, or is this meant to be just maintenance?

You can also check out CoolFire-brand solar watch chargers. They are LED gadgets where you put the watch dial down on it. It’s sort of a constant-on trickle charger for solar watches. They’re about $35 USD online (Amazon).

Paging @Racer88.

There are a bunch of older threads regarding charging solar watches (do a search on "solar charging" if you want to read through them). TLDR: for normal day to day maintenance just leave them in a well lit room, don't put them in direct sunlight, and they'll be just fine.

I went though the same thing when I bought my first few solar watches. Should I put them in the sun, in a glass of water, or maybe use a fan to cool them? Should put an LED lamp with a timer over my watch box? That seems silly to use electricity to charge a solar watch. Should I get a solar panel to charge a power bank, and then use the power bank to power a USB LED light to charge the watches? etc...

I eventually bought a solar watch that has power reserve meter. The meter has 4 segments (low to high). I just leave the watches in a room that gets good light and I make sure they aren't in direct sunlight. After about a year, I have never seen the needle of the power reserve meter ever get below the highest segment. Here's a photo for reference regarding the power reserve meter (Citizen AW7031-54A):

I have a 10 years old digital solar Casio GW-800D which sits next to a cool/shade window and the battery has never moved below "high" level. Some of my newer and more expensive Citizen watches (like a "The Citizen" series AQ1030) keep on running "low" on battery unless being put in direct sunlight or near a much brighter window. So, I guess, depending on the light transmission level through the top dial of a solar watch to reach the solar cell beneath, the efficiency of the charging circuitry, and the power consumption of a particular model, some solar watches are less demanding than others in terms of charging environment and time.