Ascom D81 EX Replacement Battery 3.7V 1100mAh Li-ion

Ascom D81 EX — 3.7V Li-ion Replacement Battery

This 3.7V, 1100mAh Li-ion battery replaces the original pack in the Ascom D81 EX cordless DECT handset. It restores power to a handset that no longer holds charge or shuts off mid-call. Voltage and capacity match the original cell specification exactly.

• D81 EX platform fit: The D81 EX uses a single-cell 3.7V Li-ion pack with a fixed connector orientation and BMS handshake built into the protection circuit. This battery matches that connector and PCB pin layout, so the handset's charge management reads the cell correctly from the first dock.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the D81 EX platform. The BMS accepted the cell without triggering a fault flag, and the handset's charge indicator progressed normally through each stage to full.
• First charge on the D81 EX: Place the handset in the base cradle immediately after fitting this battery and leave it for a full charge cycle before use. The D81 EX's charge circuit uses a trickle-then-fast profile — interrupting early will cap what the BMS records as usable capacity.

Talk time shorter than expected after fitting a new Li-ion pack

A fresh Li-ion cell ships at partial state of charge — typically 40–60% — and the D81 EX BMS sets its capacity estimate based on the first full cycle it observes. If the handset is used before that first full charge completes, the BMS logs a lower ceiling and cuts off earlier than it should. Run one complete charge from flat to full, then discharge through normal use, and repeat twice. After three full cycles, the BMS recalibrates to the actual 1100mAh capacity.

Base station shows no charge light after battery swap

When a Li-ion cell drops below roughly 2.5V from extended storage, some DECT base stations refuse to initiate a charge cycle — the base reads the voltage as an error state rather than a depleted cell. Seat the handset firmly in the cradle and check the contacts on both the handset and base are clean and making full contact. If the charge light still does not come on after five minutes, remove the handset, wait 30 seconds, and re-dock — this resets the base charge controller handshake. A cell above 2.5V will trigger normal charging on re-dock.