Ericsson DT412 V2 Cordless Phone Replacement Battery BKB 902 44/1 3.7V

Ericsson DT412 V2 / DT422 V2 — 3.7V Li-ion Replacement Battery (BKB 902 44/1)

This 3.7V, 700mAh Li-ion battery replaces the original pack in the Ericsson DT412 V2 and DT422 V2 DECT cordless phone handsets. It matches the OEM voltage rail and physical footprint, so it seats and contacts correctly in the battery compartment. Capacity is 700mAh (2.59Wh), matching the original specification.

• DT412 V2 and DT422 V2 compatibility: Both handsets share the same battery bay dimensions, contact layout, and 3.7V supply requirement. The BKB 902 44/1 pack fits either model without modification to the compartment or contacts.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the DT412 V2 platform. The handset accepted charge from the base station without error, and the BMS held within the expected voltage window across the full cycle.
• First charge on the DT412 V2 base: After installing this battery, seat the handset in the base cradle and leave it there for a full 16 hours before first use. Li-ion cells shipped in storage mode need a complete initial charge cycle to reach rated capacity — pulling the handset off early will reduce available charge on that first session.

Talk time shorter than the original battery after replacement

A freshly installed Li-ion cell often delivers noticeably less talk time on its first two or three cycles. The cell ships partially discharged for transport safety, and the BMS calibration hasn't yet tracked a full charge-to-depletion curve on your specific handset. Run three complete cycles — full charge in the base, then use the handset until the low battery indicator triggers — before judging capacity. By cycle three, the reported and actual capacity figures align, and talk time stabilises at the rated 700mAh level.

Handset not pairing with the base after battery swap

Removing the battery from a DECT handset cuts all power to the radio module, and some Ericsson DT-series units lose their base station pairing when power is fully interrupted. The handset will power on after the new battery is installed but show no line or signal. To re-register, hold the handset's menu or find button until the display enters registration mode, then trigger the registration sequence from the base station — typically a dedicated button held for three seconds. Once re-paired, the handset operates normally.