I can understand not wanting to puncture a pouch style lithium-ion cell (what most people call LiPo), but then why not go for an 18650 or 14500 battery? Same lithium ion chemistry packaged into a more traditional and durable metal can.
Although if I wasn't too confident and wanted to avoid the fires of lithium ion I'd probably gone for NiMH too.
But then the decision to put both charger types on the board when only one will ever be used? Strange, but you can't let indecision paralysis get to you I guess.
As I understood, 18650 and 14500 don't like water too much. Our 3yo will find ways to spill water onto and into it.
As for the dip: I designed the board to be multi-purpose, including new projects down the line, where I might need LiPo energy density. I think I mentioned that in the blog post.
Although if I wasn't too confident and wanted to avoid the fires of lithium ion I'd probably gone for NiMH too.
But then the decision to put both charger types on the board when only one will ever be used? Strange, but you can't let indecision paralysis get to you I guess.