 This was widely considered to be an ambient-light sensor, disabled since an early software upgrade.Color display technologies consume much more power than monochrome electronic paper (E-ink) types; Fire offer a typical battery life of 8 hours of mixed usage, while monochrome Kindles offer 15 to 30 hours' use without WiFi—"battery lasts weeks on a single charge"—with a much lower-capacity battery.The first generation of Kindle Fire devices run a customized Android 2.3.3 Gingerbread OS.