when i do a search online, this seems to be a common problem with acer laptops.
obviously you cannot remove the battery since it is built in the S3 as a lot of people have suggested to do that with removable batteries to reset it.
the issue appears to be intermittent.
sometimes it says 100% charged but other times it says 98% available (plugged in, not charging).
even though there is a lot of people complaining about this on the internet, i cannot find a solution to this issue.