About this replacement
Somfy Nina IO Touch Display & 5121348B — 3.7V Li-Polymer Replacement Battery (981642)
This 3.7V, 600mAh lithium-polymer cell replaces the OEM battery in the Somfy 5121348B remote and the Nina IO 1805251 Touch Display controller. Both devices use the same 981642 cell to power the wireless transmitter and onboard display. If your motorized shade controller has stopped responding or shows a low battery warning, this is the cell that restores it.
- 5121348B and Nina IO 1805251 compatibility: Both remotes share the same 981642 cell format — identical voltage rail, connector pinout, and physical dimensions (43.40 × 16.50 × 9.50mm). No adapter or modification is needed to fit either device.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Nina IO platform. The onboard BMS accepted the cell without fault flags, and the display powered on cleanly at full charge state.
- Post-install reconnection on the Nina IO: The Nina IO runs a mesh re-join sequence after any power interruption. After swapping the battery, leave the controller undisturbed for 60 seconds before pressing any button — interrupting that sequence forces a manual re-pair through the app.
Somfy remote going offline immediately after a battery swap
The Nina IO and 5121348B both transmit a network re-join packet the moment power is restored. If the hub doesn't acknowledge that packet — because the device moved too fast through the boot sequence or the hub was busy — the remote shows as offline. This isn't a battery fault. The fix is to hold the remote stationary for 60 seconds after install, within range of the hub, before initiating any command. If it's still offline after that, trigger a re-pair from the Somfy app — the device should appear at 3.7V and register cleanly.
New battery triggers a low-charge alert straight away
Li-polymer cells lose voltage during warehouse storage — a cell that sat for several months may read 3.4V or lower at install. The Somfy controller compares battery voltage against a threshold, and anything below approximately 3.5V can trigger the low battery indicator even on a brand-new cell. Connect the remote to its charging dock or cable for 30–60 minutes before use. Once voltage climbs above the alert threshold, the warning clears without any reset.