BTI DECT Fax Compatible Battery 3.6V 300mAh Ni-MH

BTI Dect Fax / Dect Fax Plus — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 300mAh Ni-MH replacement battery for the BTI Dect Fax and Dect Fax Plus cordless handsets. It restores wireless operation when the original cell no longer holds enough charge for practical daily use. Dimensions are 30.00 × 32.00 × 10.50mm — confirm these against the battery compartment before ordering.

• Dect Fax and Dect Fax Plus compatibility: Both handsets run on the same 3.6V single-cell NiMH architecture and share an identical battery compartment footprint, which is why one pack covers the full range.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a NiMH-compatible test rig. The cell accepted a full charge without thermal runaway and the voltage held stable under simulated RF transmission load.
• First-charge procedure for NiMH cordless packs: After installing, seat the handset in the base and leave it charging for a full 16 hours before first use. NiMH cells in cordless phones reach rated capacity only after a slow initial charge — skipping this step is the most common cause of short talk time complaints on new batteries.

Base station showing no charge or error light after fitting a new pack

A NiMH pack that has been sitting in storage can drop below the voltage threshold the base station uses to detect a valid battery. When the charger circuit sees a cell voltage too low, it may refuse to initiate a charge cycle or flash an error instead. The fix is a brief trickle charge — some bases will recover on their own after 30–60 minutes; others need the pack to be pre-charged to around 3.2V using an external NiMH charger before the base accepts it. Once the pack climbs above the acceptance threshold, the base resumes normal charging.

Range reduced on the Dect Fax after replacing the battery

DECT handsets draw a sharp current spike each time the radio transmits. If the NiMH pack hasn't completed its conditioning cycles, internal resistance is still elevated and the cell voltage sags under that RF load. The handset interprets the voltage drop as low battery and reduces transmit power, which cuts effective range. Run three to five full charge-and-discharge cycles first — internal resistance drops with each cycle and the voltage sag under transmit load shrinks accordingly.