> Also, if the batteries die, can't they just wait a few days until the ~1.5hrs/day of sunlight charges them enough to do something useful again? The explanati

> Also, if the batteries die, can't they just wait a few days until the ~1.5hrs/day of sunlight charges them enough to do something useful again? The explanation I saw was that you need a set amount of energy to warm up the batteries enough to be able to charge them effectively, and 1.5 hours of weak sunlight won't be enough to hold whatever you can charge up until the next day. You'd never accumulate. (Batteries hold less at lower temperatures.) Oh, explained better with a quote a little downthread: https://news.ycombinator.com/item?id=8609965 https://news.ycombinator.com/item?id=8609965