HYT PT580 Replacement Battery BL1806 7.4V 2500mAh

HYT PT580 / PT580H — 7.4V Li-ion Replacement Battery (BL1806)

This is a 7.4V, 2500mAh Li-ion replacement for the HYT BL1806 battery pack. It fits the PT580 and PT580H portable two-way radios. Voltage and cell count match the original pack exactly.

• PT580 and PT580H compatibility: Both models share the same battery bay geometry, contact rail, and 7.4V two-cell Li-ion architecture. The BMS handshake voltage threshold is identical across the pair, so one pack covers both variants without modification.
• Bench tested on actual hardware: We cycled this pack through PTT transmit bursts on the PT580 platform and monitored BMS response. The protection circuit held stable through repeated high-current transmit events without triggering an overcurrent cutoff.
• First insertion into the charger dock: If the dock LED flashes fault on first seating, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The PT580 dock requires a clean contact cycle to register the new BMS and begin the charge sequence.

Why the PT580 cuts out mid-transmission on a fresh BL1806

The PT580 draws a sharp current spike the moment PTT is pressed — transmit current can briefly exceed 1.5A on the BL1806's protection circuit threshold. A new cell shipped at storage voltage (typically 3.6–3.7V per cell) has a higher internal impedance than a fully charged cell, which amplifies the voltage sag under that spike. If the BMS reads the sag as a fault condition, it trips the output and the radio cuts out. Charge the pack fully to 8.4V before the first field use to bring cell impedance down to operating levels.

Bar indicator showing one fewer bar than expected after swap

The PT580 uses voltage-threshold steps to drive the bar display — each bar maps to a voltage band, not a fuel gauge reading. A new pack at storage voltage sits at roughly 7.2–7.4V, which places it in the second or third bar band even though the cells are not depleted. This is normal behaviour for a cell that has not yet been fully charged. Run a full charge cycle first; once the pack reaches 8.4V, the bar indicator will reflect actual capacity correctly.