In a backers only update this week, the team at Carbon released drawings showing some more details on their proposed solar panel design. As you may recall, the team’s solar powered wristwatch had a solar panel barely large enough, at its best, to charge a 650mAh battery in 8 hours. We brought up concerns that creating a hole for the requisite watch movement to poke through the panel would require the panel to be split into a number of smaller panels as it’s impossible (or at least very hard) to drill a hole in a monocrystaline solar panel. This would reduce the effective size of the panel due to the gaps between the sections drawing into question the original 8 hour charge time spec.
The team replied to our original article in a comment:
Looks like we weren’t quite as inaccurate as they stated. In our original assessment, we calculated that the proposed performance of the device was not too unreasonable. With the indicated 42*35mm panel, we worked out that they could charge a 650mAh battery in under the reported 8 hours if they had direct sunlight (1000W/m^2) the entire time.
Two recent developments in this recent update have shaken our confidence. Firstly, they have stated that they are going with an 800mAh battery:
This is an 18% increase in battery capacity that will purportedly be charged in the same amount of time. Also, the gaps in the solar panel both between the sections and around the border provide a 24% reduction in usable solar panel surface area.
So, with the recent developments the team plans to charge an 18% larger battery with 24% less power available in the same 8 hour time span. The team hasn’t said anything regarding an increase in charge time, but I find it very unlikely that they will be able to deliver the original 8 hour charge time.