Solar and Tritium Watches Explained

Two technologies solve the two most common hiking watch complaints. Solar charging removes charging and battery changes; tritium removes the need to press a backlight button in the dark. Neither requires any input from you once bought.

1. 1

   How solar watches work

   A photovoltaic cell under or around the dial charges a rechargeable capacitor. Casio's Tough Solar and Citizen's Eco-Drive both run indefinitely on ordinary daylight — even indoor light contributes. A fully charged Citizen Promaster runs about six months in complete darkness, so a watch left in a drawer all winter is still running in spring.

2. 2

   Solar on GPS watches is different

   A GPS watch's solar panel offsets drain rather than eliminating it, because GPS tracking uses far more power than a quartz movement. On the Instinct 2X, solar can make smartwatch-mode battery effectively unlimited with enough sun, while heavy GPS use still drains it.

3. 3

   How tritium illumination works

   Small borosilicate tubes are filled with tritium gas and coated internally with phosphor. The gas continuously excites the phosphor, producing a steady low glow with no charging from light at all. Marathon and Luminox both use this.

4. 4

   Why tritium beats luminous paint for hiking

   Standard lume must be charged by light and fades within one to three hours — useless at 3am after a night in a dark tent. Tritium is the same brightness at 3am as at bedtime. It is dimmer than freshly charged lume and it never goes out, which is the trade that matters overnight.

5. 5

   What each costs you

   Tritium dims with a half-life of about twelve years, so expect noticeably less light after a decade and usable light for roughly 25 years. Solar capacitors degrade over 10 to 20 years and are replaceable at a service centre. Both outlast the typical ownership period.

   Choosing a hiking watchWhere these features fit the decision

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