I have a solar-powered scientific calculator that is at least 10 years old, and another that might be 20 years old. I never had to change their batteries once. Even after a few years in a drawer, they’re ready to go in an instant.
With digital calipers and micrometers, batteries will drain with use and self-drain over time.
I was flipping through an industrial catalog when I came across Mitutoyo solar-powered calipers. Solar-powered calipers!
This makes a lot of sense for low-powered equipment.
I also have two solar-powered watches that never need replacement batteries, and they are always running, assuming they get enough sunlight to keep the internal battery charged.
This seemed pretty exciting, until I looked at Mitutoyo’s product specs. The calipers must be exposed to at least 60 lux of ambient lighting in order for them to be used continuously. That’s not a lot of light, but could complicate how and where the calipers are used or stored.
User reviews on Amazon confirm that the solar calipers perform best when exposed to bright lighting. Apparently, shadows cast over the face can cause the LCD display to dim or blank out.
Mitutoyo’s language about how the calipers can be powered even if uncharged at 60 lux suggests there’s an internal solar-charged battery or capacitor of sorts. In other words, you will only see best performance if the calipers are kept out and exposed to bright light to charge, or if they are only used in bright light.
In theory, these calipers would ease the frustrations associated with having to replace instrument batteries. In reality, it seems that the “solar battery” could lead to other frustrations, such as having to wait a few seconds for the calipers to charge up each time after taking them from a dark drawer.