Apple has launched a worldwide replacement program for its Smart Battery Cases built for the iPhone XS, iPhone XS Max, and iPhone XR. The affected cases might be experiencing issues like not charging or only charging intermittently when plugged into power or that these cases don't charge the attached iPhone or charges the handsets intermittently.
The Smart Battery Cases affected were manufactured between January and October 2019. Apple said the problem isn't a safety issue. You can head to an Apple Store or an authorized service provider to get your unit checked, and those eligible will get replacements for free. But the program will not extend the standard warranty coverage of the Smart Battery Case.