HME BAT400 Compatible Battery 4.8V 900mAh Ni-CD Wireless Headset

HME 400 / 430 / 900BP Series — 4.8V Ni-CD Replacement Battery (BAT400)

This is a 4.8V, 900mAh Nickel-Cadmium replacement battery for the HME 400 wireless headset system, using OEM part number BAT400. It fits the HME 400, 430, 900BP, and Com400 headsets. The cell powers both the audio circuitry and the DECT radio transmitter simultaneously during active calls.

• 400, 430, 900BP, and Com400 compatibility: These models share the same 4.8V NiCd cell configuration, connector pinout, and base station charging contact layout — the same pack works across all four without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the HME base station. The BMS accepted the cell without error, and the charge indicator progressed normally through each stage.
• First charge in the base station: Seat the headset in the base before taking any calls and let the base complete one full charge cycle. HME base stations log the new cell during this cycle — the talk-time estimate won't be accurate until that handshake finishes.

Why the HME 400 headset cuts out mid-call under combined audio and radio draw

The HME 400 runs two simultaneous loads — the audio amp and the DECT transmitter — off the same cell. At the moment a DECT packet fires, current draw spikes sharply. If the cell voltage sags below the protection threshold at that instant, the headset cuts out entirely. NiCd cells are prone to this on shallow cycles where the top-of-charge voltage never fully recovered. Running two or three complete charge-discharge cycles through the base station brings the cell to peak voltage recovery and reduces mid-call dropout.

Base station shows full charge but headset goes dead after a few minutes

This happens when a new cell arrives at storage voltage — around 4.2V for a 4-cell NiCd pack — and the base station's charge circuit interprets the quick initial voltage rise as full capacity. The cell is not actually full; it just hit the charge-termination threshold early. The fix is to discharge the headset fully in active use, then run a complete charge cycle in the base. After that first true full cycle, the base reads cell capacity correctly and the charge-full indicator reflects actual state of charge.