Microsoft warns that you should "not disconnect from AC power while the system firmware update is being applied. The rep stated that: The first round of complaints focused on Surface Pro 3 tablets that shipped with batteries manufactured by Simplo, but the newer issue affected LGC batteries instead. However, some users are still steadfast in their assertion that their Surface Pro was working fine until immediately after this update was applied. Before installing, you should ensure that your Surface Pro 3 is plugged into AC power directly, not via the Surface Docking Station, and that all USB devices and external monitors are disconnected. But a few weeks later, in mid-September, fresh complaints about battery life problems emerged from users who hadn't been affected by the earlier issues.