HME COM400 Wireless Headset Replacement Battery 4.8V 1500mAh

HME COM400 — 4.8V Ni-MH Replacement Battery (RF400)

This is a 4.8V, 1500mAh Ni-MH replacement battery for the HME COM400 wireless communication headset. It fits the COM400 directly, using OEM part number RF400. The COM400 is used in aviation and field communication environments where the headset must stay operational through full duty cycles.

• COM400 fit: The COM400 runs a 4.8V Ni-MH cell configuration with a specific connector and BMS handshake tied to the base station's charge management circuit. This pack matches that voltage rail and connector pinout so the base station recognises the cell and initiates a proper charge cycle.
• Bench tested on actual hardware: We cycled this pack through the COM400 base station and confirmed the BMS completed its handshake without error. The charge circuit accepted the pack, stepped through its conditioning phase, and reported full charge status at the correct termination voltage.
• First-cycle protocol for the COM400: Place the headset in the base station and let it complete a full uninterrupted charge before using it on a call. The COM400 base station logs the new cell during this first cycle — skipping it causes the talk-time indicator to misread remaining capacity.

Base station showing full charge but headset cuts off after short use

This happens when the replacement pack arrives at storage voltage — typically around 4.2–4.5V for a 4.8V Ni-MH pack — and the base station misreads it as already charged. The charge circuit terminates early because the delta-V detection triggers before a real full charge is reached. The headset then draws down the partially charged cells quickly under the combined load of the audio circuit and DECT radio transmitter. Run one full uninterrupted charge cycle from flat to resolve this.

COM400 headset cutting out mid-call on a new battery

The COM400 places simultaneous current demand on the battery from both the audio amplifier and the DECT radio module. During active transmission, this combined draw causes a momentary voltage sag — if the cells are not fully conditioned, the pack voltage drops below the headset's cutoff threshold and the unit shuts off. This is not a fault with the pack; it is a conditioning issue. Cycle the battery through three to five full charge and discharge sequences and the sag will reduce as the cells reach rated capacity.