I have a small collection of Seiko watches and I wanted a representative from the Kinetic range but I had read that there were difficulties keeping them charged. Fortunately, I think I have a fix, at least for the SKA787 (shown left).
The Seiko SKA787 is a comparatively recent version of a kinetic watch (I purchased it new in 2020) but kinetics have been in evolution since the first kinetic watch in 1986.
Kinetic watches contain a unique movement in which the movement of the wearer charges the watch. “That is nothing new” I hear you say. Yes, automatic mechanical watches go back as far as 1776 or early 1777 (Wikipedia) where the movement of the wearer causes a weighted pendulum or rotor to wind a spring which in turn powers the watch. In those days of course it was a pocket watch.
But a kinetic watch is different. A rotor which swings through the movement of the wearer’s wrist, spins a tiny generator, at up to an amazing 10,000 RPM, and charges a capacitor (think watch battery). A fully charged capacitor will power a watch for up to 6 months, but it usually requires daily, or at least regular weekly wear, to keep it charged. For watch collectors, who share wrist time between many watches, that can be a problem.
There are many, many articles and forum posts online about ways of charging kinetic watches using toothbrush chargers. Think of charging pads that charge mobile phones or watches (although they don’t work with kinetics). The photo on the left is a homemade setup found on Watchuseek utilising a Braun 4728 charger. The toothbrush charger can connect remotely with the charging coils in a kinetic watch and charge the capacitor. I say “can” because although some have had success using a toothbrush charger to charge their kinetic watch (most commonly the Braun 4728 model shown here) many others have been un-successful. Seiko at one stage produced their own dedicated kinetic charger but they ceased production and used versions now command up to A$850 online.
There are plenty of descriptions online describing minute variations to placement and time in
order to get the toothbrush charger to work. In my case the Braun 4728 (I also tried a Braun 3757) did not charge the SKA787 despite patiently testing multiple charging positions for at least 24 hours each. Kinetic watches have a handy charging scale built in so it is easy to see if the process is working. I came to the conclusion that the charging power emitted by the Braun charger(s) was simply not getting through to the coils in my SKA787. (see photo right)
I then came across some examples online of a Phillips Diamondclean Toothbrush Charger (HX9100) successfully charging kinetic watches. What appealed to me was that the charger was designed to accept a thick glass cup in which the rechargeable toothbrush was placed. So it appeared that the electrical charge could travel further than with other chargers. The Phillips Diamondclean Toothbrush Charger is still in production and can be purchased for A$35 plus postage online.
I had already spent over A$100 trying to charge my kinetic watch but took the plunge with the Phillips charger, and purchased from Statewide Appliance Spares in Adelaide, South Australia.
I had immediate success. I plugged the charger into an Arlec Watt Meter and got an idle power consumption of around 0.4 watts. When I placed the watch vertically in the metal charger (6 o’clock down) the power consumption of the charger immediately went up to 2.5 watts, a sure sign that the charger was working, and the watch was consuming power.
Seiko kinetic watches have a charging indicator on the dial. You press a small button on the side of the case and the second hand quickly swings forward. When the second hand swings forward 30 seconds, you apparently have a full 6 months of charge in the capacitor. A 5 second swing indicates less than 7 days and that was the reading on my watch before this process started.
The following morning (with the watch left on charge overnight) the charging scale showed a 20 second swing which is equivalent to around 1 months charge. 24hrs later on the charger and I had a full 30 second swing so, subject to any capacitor memory issues, I believe my watch is fully charged. I will now wear it for a few days and check the charge regularly. It may be necessary to place the watch back on the charger to get the capacitor used to full charge state.
Conclusion: The Phillips Diamondclean Toothbrush Charger (HX9100) has proven very effective in charging my SKA787 Kinetic watch and will allow me to keep a kinetic in my collection.
Will it work as effectively with other kinetics? I am guessing the answer is yes, but maybe I need to purchase a couple more kinetics from different eras to check it out. Purely in the interests of scientific analysis of course 😇
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