Galaxy S4 Battery Issue : Check Your Serial Number Here
as you know some of the Galaxy S4's batteries are defective (batteries are swelling), especially in Europe. Samsung acknowledged the problem and offers free replacement.
Here's something from Samsung (not official yet though AFAIK) :
You can check the Serial Number of your battery. If the S/N starts with BD1D
and the date is in the range of 401 - 529
(1st april - 29th may), it's probably a defective battery.
Any battery with S/N between BD1D401XX and BD1D529XX needs replacement.
Hope this will help some of you.