About this replacement
Ring Video Doorbell 2nd Generation — 3.8V Li-Polymer Replacement Battery (S1)
This 3.8V, 4200mAh Li-Polymer cell replaces the original S1 battery in the Ring Video Doorbell 2nd Generation (model 5UM5E5). It fits the removable battery module that slides out of the doorbell base for charging. Voltage and capacity match OEM spec exactly — 3.8V nominal, 15.96Wh.
- Video Doorbell 2nd Gen and 5UM5E5 fit: Both model names reference the same hardware platform. They share an identical battery bay geometry, connector polarity, and 3.8V BMS handshake — one cell covers both.
- Bench tested on actual hardware: We cycled this cell through motion-triggered recording loads on the Video Doorbell 2nd Gen. The BMS held stable under the combined current spike from the IR LEDs, processor, and WiFi radio firing simultaneously on a motion event.
- Firmware registration after install: On first install, power cycle the doorbell once through the Ring app. The firmware must register the new cell before motion-triggered clips log correctly to cloud storage — skipping this step can cause missed recordings even when the doorbell appears online.
App showing 0% or an incorrect charge level after battery swap
The Ring Video Doorbell 2nd Gen reads battery level using a voltage-threshold indicator — not a fuel gauge IC. When a new cell is installed at a mid-state-of-charge, the firmware maps that voltage to an estimated percentage that may read incorrectly until calibrated. Run the battery down to the low-battery alert, then charge it fully in the removable module using the included cable. After one complete cycle, the voltage thresholds align and the app percentage tracks accurately.
Recording stops mid-clip or motion events are missed entirely
On a weak WiFi signal, the doorbell's radio repeatedly reconnects during a clip, drawing a current spike that can trip the BMS protection circuit mid-recording. This shows up as truncated clips in the Ring app history or gaps where motion was clearly detected but no video saved. Move the router closer or add a Ring Chime Pro as a signal extender to reduce reconnect frequency. The BMS resets automatically — confirm signal strength in the Ring app's Device Health screen is reading "Good" or above.