Gigaset SL800H Pro Compatible Battery 3.7V 950mAh Li-ion

Gigaset SL800H Pro Series — 3.7V Li-ion Replacement Battery

This is a 3.7V, 950mAh Li-ion replacement battery for the Gigaset SL800H Pro cordless DECT handset. It also fits the SL750H Pro, SL610 Pro, SL400H, and four additional models in the same handset family. The original battery degrades with daily charge cycles — this replaces it like-for-like at the same voltage and capacity.

• SL-series handset compatibility: These handsets share a common Li-ion cell form factor, connector pinout, and BMS communication protocol across the SL400H through SL800H Pro range. The same 3.7V rail feeds the DECT radio module, DSP, and display — swapping a cell from one model to another in this family does not require reconfiguration.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Gigaset SL-series handset. The BMS accepted charge immediately from the base station, voltage held steady through transmission bursts, and no protection cut-off events were triggered under normal RF load.
• First charge after install: Li-ion cells in DECT handsets can sit in storage at partial state of charge. After fitting, seat the handset in the base and leave it for a full uninterrupted charge cycle before use — this lets the BMS calibrate its state-of-charge tracking accurately.

Talk time shorter than expected after fitting a new battery

A Li-ion cell that has been stored for several months will have a lower initial capacity than its rated 950mAh. The BMS may also have an inaccurate charge level estimate on the first cycle. Run two to three full charge-and-use cycles and the cell will reach close to rated capacity as the BMS recalibrates. After three cycles, a resting voltage of 4.1–4.2V at full charge confirms the cell is performing correctly.

Handset not re-pairing with base station after battery swap

Removing the battery from a DECT handset cuts power completely — some Gigaset models lose their base station pairing when this happens. The handset retains pairing in volatile memory, and a full power loss clears it. Re-register the handset manually from the base station menu using the standard DECT registration sequence. Once paired, the handset resumes normal operation without any further steps.