About this replacement
HME 400 / 430 / 900BP / Com400 Series — 4.8V Ni-MH Replacement Battery (BAT400)
This is a 4.8V, 1200mAh Ni-MH replacement battery for the HME 400 wireless headset system. It uses OEM part number BAT400 and fits the 400, 430, 900BP, and Com400 models. The pack powers the headset's audio and DECT radio circuits.
- 400 / 430 / 900BP / Com400 compatibility: These models share the same 4.8V four-cell Ni-MH pack format, connector pinout, and charge termination behaviour through the base station — one battery works across all of them.
- Bench tested on actual hardware: We cycled this pack through the HME base station and confirmed correct charge termination at full capacity. The BMS handshake completed without error and the base station's charge indicator behaved normally throughout.
- First charge in the base station: Dock the headset before taking any call and let the base station run a complete charge cycle. DECT headsets log the new cell through the base — skipping this step means the talk-time estimate will be inaccurate and the headset may cut out under combined audio and radio draw.
Base station not recognising the new pack after installation
HME base stations use a charge handshake to log a new Ni-MH cell before reporting status. If the pack ships at storage voltage — typically around 4.0–4.2V for a four-cell Ni-MH — the base may not initiate a full charge cycle automatically. Remove the headset, reseat it firmly in the cradle, and leave it undisturbed for at least 90 seconds. This allows the base to detect cell voltage and begin the recognition sequence. If the charge LED still does not respond, check that the cradle contacts are clean and making solid contact with the battery terminals.
Headset cuts out mid-call even though the base showed a full charge
The HME 400 draws current from two circuits simultaneously — the audio amplifier and the DECT radio transmitter. Combined, this draw can cause voltage sag on a freshly installed Ni-MH pack that has not completed its first conditioning cycle. The base station's charge indicator reads resting voltage, not loaded voltage, so a pack can show full and still sag below cutoff under live call conditions. Run two to three complete charge-and-use cycles before relying on the headset in a high-demand shift. After conditioning, the pack will maintain voltage above the 4.2V loaded threshold the radio module requires to stay on.