Unify OpenStage SL4 Compatible Battery 3.7V 830mAh Li-ion

Unify OpenStage SL4 / OpenScape SL5 — 3.7V Li-ion Replacement Battery

This 3.7V Li-ion battery at 830mAh (3.07Wh) replaces the original cell in the Unify OpenStage SL4, OpenStage SL4 professional, OpenScape SL5 professional, and compatible variants. It slots directly into the handset battery compartment and restores power to the DECT handset. Physical dimensions are 52.95 × 35.10 × 4.50mm — check your existing cell before ordering if unsure.

• OpenStage SL4 and SL5 platform fit: These handsets share the same battery bay geometry and voltage rail across the standard and professional variants. The cell interfaces directly with the handset's charge management circuit — no modification needed.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on DECT handset test rigs. The protection circuit engaged correctly at low-voltage cutoff and the charge circuit accepted current from a standard base station without error flags.
• First-charge protocol for Li-ion DECT handsets: After fitting this cell, seat the handset in the base station and leave it undisturbed for a full charge cycle — typically 8 to 12 hours — before using it. Li-ion cells shipped in storage-state charge need a complete first cycle to allow the handset's fuel gauge to calibrate correctly.

Talk time shorter than the original battery after replacement

A new Li-ion cell ships at a reduced state of charge — typically 30–50% — and the handset's internal charge tracking starts from that point. The fuel gauge in the OpenStage SL4 calibrates across full charge and discharge cycles. Until two or three full cycles complete, the handset may underestimate remaining capacity and shut down earlier than expected. Run the handset down until the low-battery alert triggers, then charge fully to 4.2V — repeat this two to three times and talk time stabilises.

Handset not pairing after battery swap

Removing the battery from a DECT handset cuts all power to volatile memory, which can erase the stored base station pairing on some OpenStage SL4 units. The handset will power on but show no signal or fail to register with the base. You will need to re-run the DECT registration sequence — hold the paging button on the base station, then initiate pairing from the handset menu within 60 seconds. Once paired, the link is stored to non-volatile memory and survives future battery changes.