This is a known issue, and it will change in the next update. The issue occurs when the time is over 24 hrs.lays a completely wrong time left or it shows unreadable characters

Our fuel gauge, that measures capacity, learns with every charge.  So, it becomes more accurate over time.  To avoid the initial learning process, we ‘taught’ the battery through programming what it should show.  However, if a battery starts its life at low charge, this does not work.  Therefore, you get an issue like you are seeing.  There is nothing wrong with his battery.  The battery is just learning, and it will come right after 3-4 charge cycles. In the meantime, the most important factor is the runtime and how long his light lasts.

Yes, so that’s good news for our friends in the North that use GW lightsets with their snowmobiles.

The battery can be charged at up to 30W from a USB PD charger.  From other chargers it can charge but as every charger is different there are not accurate specifications for this. We can say that QC will charge at 17W (12V) and Apple Chargers also charge at their dedicated charge speed. 

They are USB PD chargers.
Have a look at the product’s page for a full list of specs and charging times
https://www.luminous.bike/product/gloworm-fast-charger-g2-0/

We no longer include a rubber cap anymore. They were only aesthetic, so nothing to worry about.