Battery operated charger for Solar Watch

datiLED

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Because I always wear long sleeve shirts at the direction of my dermatologist, my solar watches rarely have the opportunity to get a quality charge. Being disappointed by the quality and/or price of solar watch chargers, I decided to have a go at making my own. After SEVERAL prototypes and redesigns, I decided to go with battery power instead of a USB or wall charger. The end result is the SOL-TIME solar watch charger**. Powered by a single AA or CR123 cell, a Nichia HS LED is focused onto the watch dial and rapidly charges the cell (and lume) at 22mA. Here the SOL-TIME is charging my Citizen Promaster Eco-Drive. This watch really lives up to the nickname of "Lume King". Since the pictures were taken, I have added a 3D printed cover to protect the circuit and provide and strain relief for the negative lead.

Charging my watch in ambient light.
IYuupMn.jpg


An overhead shot showing the intensity of the light on the solar cell.
qOBjcwa.jpg


In the dark. As a bonus (or negative) the light from the charger is sufficient to easily navigate in the dark room.
If I wanted to charge the watch over night, I would need to 3D print a cover or shield to contain the light.
v6qEoV1.jpg


I had considered 3D printing a housing that would have the LED face upward, so I could place the watch face over the light. However, I chose to go with this simple design as I only have two solar watches at this point. If I end up getting a Seiko Solar Tuna or Citizen Orca, I may revisit this project and cook up something more elegant. For now, this works for me and has been doing a terrific job of charging the watch.

**I decided to get creative with the PCB artwork this time, as I was really impressed with the detail that the fabricators were capable of.
 

archimedes

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Very cool :cool:

Does it attach with magnets, or what looks like some sort of plastic clips ?
 
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Lynx_Arc

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Almost ironic...... a watch bought to not have to change the battery you have to power it with a changeable battery.
Now you need a solar charger to charge the battery in the solar charger.
 

datiLED

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Very cool
:cool:

Does it attach with magnets, or what looks like some sort of plastic clips ?


Magnets. Just like my battery drainers.

Almost ironic...... a watch bought to not have to change the battery you have to power it with a changeable battery.
Now you need a solar charger to charge the battery in the solar charger.

:grin2: Yeah, that is kind of funny now that you mention it. I loved the look and size of the watch, and never really thought about the fact that it was solar powered until I had it for a while.
 

Lynx_Arc

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:grin2: Yeah, that is kind of funny now that you mention it. I loved the look and size of the watch, and never really thought about the fact that it was solar powered until I had it for a while.
I once had a self rewinding watch that if you didn't wear it almost every day it the spring would lose power. I switched to these cheapo Casio watches as they use common 2025 batteries that I can get for about a dollar each and last 5-10 years in use. I typically have to replace the watch band before the first battery dies. I do think however that a solar watch would be good if it could store power for 2-3 days AND run an atomic clock radio reception on it for accuracy. I've only had one watch that I considered accurate and it was a mid 70s Sensor watch with tritium backlight and I would reset it twice a year for DST and the most it was off was 6 seconds.
 

Lynx_Arc

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I just remembered I have something already built that could do that, a small power bank and a USB LED light module that is dimmable. I have 90 degree M/F adapter on it that allows the whole thing to tail stand and flood below with light.
 

tjswarbrick

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Looks cool, and a creative solution to an annoying problem.
But, no battery worries is the reason I moved to mostly solar and automatic watches.
(Just wrecked my second Skagen trying to swap a battery out.)

I have 3 solar Citizens. The oldest one (Titanium) takes and holds the best charge. Just leaving it on the nightstand in a transparent-cover watch case is enough to keep it charged indefinitely. I thought it lost time once, but it turned out I didn't close the crown after adjusting the date. The other two occasionally start to slip. I just set them on a windowsill or near the patio door - without the curtain in the way - for a couple hours, and even on a cloudy day they'll last at least a full weekend.

Solar Casio G-Shock has never lost time or run out of juice, and one time I left it my my backpack for nearly a week after a trip. (It puts itself into standby at night, but wakes up with light or motion in the morning.) It is supposedly able to follow the atomic clock, though I've never been successful getting it to do so. I just set it to my mobile phone time when I change time zones, and switch in and out of Daylight Savings twice a year. It's over 10 years old now, always swims with me, and has never missed a beat.
 

Dave_H

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I have a couple of small LED booklights with adjustable heads which would probably work fine. One has three light settings (touch control). It runs on 1xAAA, not ideal but works. You could solar charge NiMH cells to power something like this; overall low efficiency but would do the job.

Somewhere around I also have a very small magnetic gooseneck worklight using a single 5mm LED. Its head could be pointed very close to a watch face. Regrettably some run on 3xLR44 which is not good battery economy.

BTW, what colour of LED would most efficiently charge these watches? If white, which tint?


Dave
 

Olumin

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Just keep in mind folks that the capacitors inside solar powered watches will eventually go bad as well and should be replaced after 10 years or so. You will notice the cell is starting to go bad when it no longer holds a decent charge. I would strongly recommend having it done by an officially certified service center or certified independent watchmaker. Please do not attempt to do it yourself, in most cases this is more complex then a simple battery change.

I for my part simply charge solar watches on a window sill. I do usually wear a GPS solar watch from Citizen, as it is handy for setting the time on other clocks and watches due to it never being more then about 1 second off.
 
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