Please try removing the top of your KaiLab robot (Yellow lid) and use your finger to rotate the battery while in the holder.
This will help remove any dirt/debris between the battery and the contacts in the battery holder.
In some cases, the battery may need to be removed to get more access to the battery and battery holder contacts for cleaning. You can remove the battery by cutting the zip tie (this will not affect your warranty) that holds it in place.
Once you have unobstructed access, using a contact cleaning solution on a cotton bud/Q-tip, run the cotton bud/Q-tip in a circular motion along the surface of the battery contacts and terminals in the holder to ensure that all dirt and debris have been removed.