Agfeo Dect 20 Replacement Battery 3.6V 400mAh Ni-MH

Agfeo Dect 20 — 3.6V Ni-MH Replacement Battery (McNairF6M3EMX)

This is a 3.6V, 400mAh Ni-MH replacement battery for the Agfeo Dect 20 cordless DECT handset. It slots into the handset battery compartment and restores wireless call and standby function when the original pack has degraded. Capacity is 400mAh (1.44Wh), matching the original specification.

• Agfeo Dect 20 fitment: The Dect 20 handset uses a compact single-cell Ni-MH pack at 3.6V — the connector orientation and cell dimensions (49.60 x 33.62 x 6.70mm) match this unit directly. No modification needed.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Ni-MH test rig. The cell accepted a full charge without thermal runaway and held voltage within the expected window across five conditioning cycles.
• First installation charge on Ni-MH: After fitting, seat the handset in the base and leave it for a full 16 hours before using it. Ni-MH cells shipped in storage state need a slow initial charge to reach rated capacity — skipping this step means noticeably shorter talk time from day one.

Range drops after battery swap on the Dect 20

DECT transmit power draws a sharp current spike each time the handset sends a radio burst. A Ni-MH cell that hasn't completed its conditioning cycles has higher internal resistance, which causes voltage to sag under that RF load. When voltage sags, the handset pulls back transmit power to stay within its operating range — and coverage shrinks. Run three to five full charge-discharge cycles and internal resistance falls, voltage holds steadier, and range returns to normal.

Base station not charging the new battery — error light stays on

Agfeo base stations check for a minimum voltage at the charging contacts before committing to a charge cycle. A Ni-MH cell that has sat in storage can drop below that threshold — typically under 3.0V — and the base reads it as a fault rather than a flat battery. To recover it, place the handset in the base and leave it undisturbed for 30 minutes. The trickle circuit in the base will nudge voltage up enough for the main charge cycle to engage. If the error light clears and the charge indicator shows active, the pack is recovering normally.