Just in case any one missed this one.

Battery bothers affecting up to 30% of Galaxy S4 users.

Samsung has packed a whole lot of tech into its flagship Galaxy S4 smartphone but it seems to have let some battery issues slip through the cracks.
Following reports of widespread battery problems, which seemed to particularly affect German Galaxy S4 users with as many as 30% experiencing issues according to German site MobiFlip, Samsung has announced that it will replace faulty batteries free of charge.
The issues range from a fast-draining power pack to the lithium-ion units actually swelling up and pushing against the case of the phone, something we've seen BlackBerry devices do in the past.
The statement was made to TrustedReviews and ends by assuring customers that Samsung remains "committed to providing the best possible user experience for our customers."
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The full statement reads: "We are aware of this issue, which has affected a limited number of customers.
"We ask all affected customers to please visit their nearest Samsung Electronics service centre, where they can receive a replacement battery for free of charge. We remain committed to providing the best possible user experience for our customers."
If you find that your Samsung Galaxy S4 battery is playing up, Samsung urges you to bring it in to your nearest Samsung Electronics service centre, where a replacement battery will be provided.
Whether the new batteries will be any more reliable is unclear, but at least you can always go back and get it replaced again if you're unlucky enough to have two faulty batteries. Source