Question about Stx Electric SUP Pump incl. battery

Is actually permanently installed. However, you could replace the battery, it is connected with a plug (not permanently soldered).
On my first one, the battery was completely flat after a year and only about three charges and could no longer be charged. You can certainly get a working replacement battery in a model shop or similar. I think I was told on enquiry that there are no replacement batteries available to reorder.