Ascom Talker 9D24 MKII Compatible Battery BKB 902 3.7V 700mAh Li-ion

Ascom Talker 9D24 MKII — 3.7V Li-ion Replacement Battery (BKB 902 44/1)

This 3.7V 700mAh Li-ion cell replaces the original battery in the Ascom Talker 9D24 MKII, Messenger 9D24 MKII, Raid2 Talker MKII, and Grade 3 handsets. It matches the OEM part numbers BKB 902 44/1, BKBNB 902 44/1, BKB 902 44/1R1A, 660087, and 660088. Physical dimensions are 59.10 × 41.66 × 13.16mm — confirm fit before ordering if your handset has had a prior non-OEM replacement.

• Talker and Messenger 9D24 MKII platform: These handsets share a common battery bay geometry, connector pinout, and BMS voltage threshold across the Talker, Messenger, and Raid2 MKII lines, which is why a single cell covers all listed variants.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 9D24 MKII platform. The BMS accepted the cell without fault codes, held charge correctly in the base station, and delivered consistent voltage across the discharge curve.
• First-charge protocol on DECT handsets: After fitting this battery, seat the handset in its base and leave it for a full 16 hours before first use. Li-ion cells shipped in storage state need a complete slow charge to reach rated capacity — pulling the handset off the base early will leave the cell under-initialised.

Talk time shorter than original battery after replacement

A freshly fitted Li-ion cell does not always deliver full capacity on the first cycle. The cell ships partially charged and the BMS calibrates its state-of-charge tracking over the first two to three full cycles. Discharge the handset until it signals low battery, then return it to the base for a full charge — repeat this three times. By cycle three, the BMS will have an accurate charge map and talk time will stabilise at the rated level.

Handset not pairing with base after battery swap

Removing the battery from a DECT handset cuts all power, and some 9D24 MKII units lose their base station pairing when that happens. The handset retains pairing data in non-volatile memory, but a full power interruption can corrupt the stored registration. Re-register the handset from the base station menu — on the 9D24 MKII, hold the paging button on the base for five seconds, then follow the on-screen pairing prompt on the handset within 60 seconds.