Walker W400 Cordless Phone Replacement Battery 3.6V 600mAh

Walker W400 / W9001 — 3.6V Ni-MH Replacement Battery

This 3.6V 600mAh Ni-MH battery replaces the original pack in Walker W400 and W9001 cordless phone handsets. Both models share the same voltage rail, cell format, and connector, so one battery covers the pair. Capacity is drawn from product data: 600mAh (2.16Wh).

• W400 and W9001 compatibility: Both handsets run on the same 3.6V NiMH cell stack with an identical footprint and contact orientation. The voltage rail and charge acceptance threshold are the same across both units, so no adapter or modification is needed.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a NiMH-capable analyser. The BMS accepted charge without interruption and voltage held steady through five full cycles, confirming the cell is matched to the 3.6V cordless phone charge circuit.
• First-charge protocol for NiMH cordless packs: After fitting this battery, place the handset in the base and leave it for a full 16 hours before first use. NiMH cells in cordless phones are slow-charged by the base station — skipping this step leaves the cells at partial formation and talk time will fall short of the rated 600mAh for the first several cycles.

Base station showing no charge light on a new NiMH pack

NiMH batteries sit in storage before they ship, and the cell voltage can drop to a point where the base station's charge controller refuses to begin a charge cycle. Walker cordless bases typically require the pack to present at least 3.0V before the charge circuit activates. If the base shows no light or an error indicator, the pack needs a brief trickle to lift it above that threshold. Remove the handset, wait 30 seconds, and reseat it firmly — this resets the base's detection cycle. If the base still does not respond, check that all three contact pins on the handset are clean and making full contact with the cradle.

Range drops noticeably after fitting the replacement battery

A NiMH pack that has not completed its conditioning cycles will show voltage sag under the RF transmit load of the DECT radio. When the transmitter fires, current draw spikes and an under-conditioned pack cannot hold the voltage rail steady — the handset compensates by reducing transmit power, which cuts usable range. This is not a fault with the battery or the handset. Run three to five full charge-discharge cycles and the cells will stabilise at their rated capacity. After that, the voltage under RF load stays within the operating window and range returns to normal.