Pi-Ener-lite: Compact UPS solution for the Raspberry Pi uses an 18650 battery

Single-board computers—particularly Raspberry Pi models—are remarkably versatile, handling everything from home media streaming to sensor data logging and actuator control. In mission-critical applications, however, maintaining continuous operation during power drops or full outages is paramount. The  Pi-Ener-lite, currently listed on Tindie for $35, provides a compact uninterruptible power supply (UPS) specifically tailored for Raspberry Pi Zero boards.

A key advantage of the design is its reliance on a standard 18650 lithium-ion cell. While less common than standard AA batteries, 18650s are widely available from various brands. Neither the 18650 cell nor the required CR1220 coin cell is included in the package. The CR1220 powers an integrated DS1307 real-time clock (RTC), ensuring the Raspberry Pi Zero retains accurate time metadata even after a complete power cycle—a crucial feature for log files and scientific measurements.

Battery life naturally depends on system load, cell capacity, and boost-converter efficiency (stepping up 3.7V to 5V). As a baseline, a 12 Wh cell (3,200 mAh at 3.7V) powering a 1W workload yields roughly 11 hours of runtime. The board supports simultaneous charging and discharging (pass-through power) and connects directly to the Pi Zero via pogo pins, which handle both power transmission and data communication. Onboard LEDs provide quick visual feedback on current battery levels and operating status.