I just found that they are selling calipers on Aliexpres which have a small solar panel to power them. And they also have a battery to power them when used in poor light. Some use LR44 batteries and some use cr2032 batteries.

And some are stainless steel and some are carbon fiber.

And my question is whether the carbon fibre one will last under light usage? And will they stand up to being used every day?

And any comments on which battery is the one to buy. The lithium battery is a higher voltage and that could be a problem with a solar cell meant to be used with a 1.5 V battery.

Dan