DIY Raspberry Pi UPS – An Uninterrupted Power Supply to Keep your Pi Safe during Power Failure
Amazon.com: XBERSTAR 18650 Power Bank case,Li-Ion Battery Storage Box -18650 Holder for Uninterrupted Power Supply UPS DIY Battery Special Plastic DIY kit (Black) : Electronics
DIY Mini UPS for WiFi Router / Modem : 12 Steps (with Pictures) - Instructables