We have worked very hard over the past two years to ensure that we could offer a product that was safe, affordable and easy to use. There are a number of reasons for making the battery non-replaceable.
1. It would add bulk. We wanted to keep the design as tight as possible without adding additional weight and bulk. Including a compartment that could be opened would require us to add parts that could inadvertently open up or fail, which would defeat our goal of keeping it simple.
2. The most important reason for making it non-replaceable is that after a year of clicking your cap on and off pens, the plastic is going to get worn down and the fit won't be as tight anymore. This means that your cap could come off easily in a bag or in your pocket, which would, again, make it less safe and straight forward to use.
We are working on getting a recycling option going for all our users that would allow them to return their used caps to us for recycling. Watch this space and if you have any queries, don't hesitate to email us at firstname.lastname@example.org.