About this replacement
Entel HT640 / HT642 / HT644 / HT649 Series — 7.4V Li-ion Replacement Battery (CNB750E)
This is a 7.4V, 2000mAh lithium-ion replacement battery for the Entel HT640, HT642, HT644, and HT649 handheld two-way radios. It uses OEM part number CNB750E and fits the same battery bay with the same contact layout. Voltage and capacity match the original Entel specification exactly.
- HT640 series compatibility: The HT640, HT642, HT644, and HT649 share the same 7.4V battery bay, contact strip geometry, and BMS handshake protocol — one pack covers the full platform without modification.
- Bench tested on actual hardware: We ran this pack through charge, discharge, and PTT transmit-surge cycles on the HT640 platform. The BMS handled the transmit current spike without tripping and accepted dock charging from rest voltage without fault LED.
- First insertion into the dock: If the dock shows a fault LED on first seating, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The Entel dock requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the HT640 cuts out mid-transmission on a new CNB750E pack
A new lithium-ion cell ships at storage voltage — typically 3.6–3.7V per cell, putting the pack around 7.2–7.4V open-circuit. That reads fine at idle, but the HT640's transmit circuit draws a sharp current spike the moment PTT is pressed. If the BMS interprets that spike as an overcurrent event before the cells have been through a full charge cycle, it cuts power momentarily and the radio drops. The fix is to charge the pack fully before the first transmission shift, not straight from the box.
Bar indicator showing one fewer bar than expected on a new pack
The HT640 uses a voltage-threshold bar indicator — no fuel gauge chip, just voltage steps mapped to bar segments. A new CNB750E at storage voltage sits at a threshold boundary, so the radio may display one bar fewer than a fully charged pack. This is not a capacity fault. Charge the pack to completion — the charger dock green LED confirms full charge — and the bar indicator will reflect the correct voltage level on next power-on.