Sorry to hear you are having a charging problem with your G-ZIP.
As with all rechargeable batteries, they do have a service life that will vary depending on amount of use, recharging habits, etc. Unfortunately due to liability issues, we do not sell replacement batteries for our G-Project speakers. In addition, due to warranty and liability issues, our speakers are not intended to be repaired or modified by our customers.
If you can send us a direct email (firstname.lastname@example.org), I will be happy to open a ticket and review some details to see if we can get it resolved for you.
The reason I am asking you to send a direct email rather then continuing the process here is that we will need your contact information and we prefer that is not posted here in a public thread.