Swatch Solar

Heard of Swatch Solar, but this is the first time I saw it being sold on eBay. Naturally, I flagged it on my watchlist, ready to put in the winning bid.

Then I did some research. Unlike other solar-powered watches, Swatch Solar doesn't really run on solar power alone. Light hits the watch face, and solar energy is used to recharge an internal battery, which powers the movement. Well, technically not a battery, but more of a mini capacitor. Instead of storing electrical energy chemically like rechargable batteries, the mini capacitor stores electrical energy physically.

And unlike the Swatch Autoquartz, where the battery is not user-replaceable, you can swap out the Renata GC 1120 on the Swatch Solar when it dies. You'll need to have the right tool though. Instead of the usual battery cover with a slot, this one has three small indentations arranged in a triangle. I guess this is prevent people from putting in the wrong type of battery. Thing to note - the factory that produces these GC1120 mini capacitors have stopped production 15-20 years ago. That's probably the end of the line for the Swatch Solar then.

Cool fact - the Swatch Autoquarz uses a Panasonic MT920.