From the article: "After the Kaby Lake upgrade, the other major improvement is the move from a 56wHR 4-cell battery to a slightly greater capacity 60wHR model.

From the article: "After the Kaby Lake upgrade, the other major improvement is the move from a 56wHR 4-cell battery to a slightly greater capacity 60wHR model. That doesn't sound like much, but Dell now claims an astounding 21 hour battery life for the 1080p version of the XPS 13. That claim was largely borne out in Ars testing of that model, which managed to last for over 18 hours in Ars' standard Wi-Fi browsing test."