DeTeWe 650c Cordless Phone Compatible Battery 3.7V 800mAh

DeTeWe 650c / 632d Series — 3.7V Li-ion Replacement Battery (DK512009)

This is a 3.7V 800mAh Li-ion replacement battery for the DeTeWe 650c and related cordless DECT handsets. It fits the 650c, 632d, 622d, and 612d, plus eight additional models that share the same battery footprint and connector. Capacity is rated at 2.96Wh, matching the original specification.

• 650c / 632d series compatibility: These models share the same 3.7V single-cell Li-ion rail, connector pinout, and BMS communication protocol. The handset firmware accepts the DK512009 pack without triggering a fault state, so the charge indicator behaves normally from the first base station cycle.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 650c base station. The BMS reported a clean state-of-charge handshake, the base LED moved from charging to standby as expected, and voltage held stable under RF transmit load.
• First charge on a Li-ion DECT handset: After fitting this battery, seat the handset in the base and leave it there for a full charge cycle before first use. Li-ion cells in low-standby-draw devices like DECT handsets can arrive partially discharged from storage — a full first charge lets the BMS calibrate its capacity estimate correctly.

Talk time shorter than the original after replacing the 650c battery

A new Li-ion cell in a DECT handset often shows shorter talk time for the first two or three cycles. This happens because the BMS has not yet mapped the full charge window of the new cell — it cuts off conservatively until it logs a few complete cycles. Run the handset down to the low-battery warning and then charge it fully two or three times. By the third full cycle, the BMS recalibrates and talk time stabilises at the rated capacity.

DeTeWe 650c handset loses pairing after battery replacement

Some DECT handsets store pairing data in volatile memory that is held by the existing battery charge. When the old cell is fully discharged or the battery is removed for more than a few seconds, that memory clears. The handset then boots without a registered base station. To fix this, hold the handset's paging or find button on the base until the handset enters registration mode, then complete the pairing sequence — on most DeTeWe bases this takes under 30 seconds.