EADS THR9 Compatible Battery BLN-6 3.7V 5700mAh Li-ion

EADS THR9 / THR9i / THR9 C-30 — 3.7V Li-ion Replacement Battery (BLN-6 / BLN-5i)

This is a 3.7V Li-ion replacement battery rated at 5700mAh (21.09Wh), built to fit the EADS THR9, THR9i, and THR9 C-30 handheld transceivers. It replaces OEM part numbers BLN-6 and BLN-5i. The battery slots into the same footprint as the original and connects through the same multi-pin interface on the radio body.

• THR9 platform compatibility: The THR9, THR9i, and THR9 C-30 share the same battery bay dimensions and connector pinout, which is why a single cell covers all three variants. The BMS handshake voltage thresholds are identical across this family, so the radio's charge management circuit accepts this pack without modification.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on the THR9 platform. The BMS held cell voltage within spec under simulated PTT burst loads, and the protection circuit tripped correctly at the low-voltage cutoff threshold before the cell reached damaging depth.
• First insertion into the charger dock: If the dock shows a fault or error LED on first insertion, remove the battery, wipe the gold contact pads on both the battery and dock with a dry cloth, and reseat firmly. The THR9 charger requires a clean contact cycle to complete the initial BMS handshake before it will begin charging.

Why the THR9 cuts out mid-transmission on a new battery

The THR9 draws a sharp current spike the moment PTT is pressed — transmit current significantly exceeds receive current. If the BMS detects this spike as an overcurrent event, it trips the protection circuit and cuts power to the radio. This is not a fault with the battery; it is the BMS responding to a load it has not yet conditioned to. After two or three full charge-discharge cycles, the BMS internal resistance characterisation settles and the cutoff threshold calibrates to the actual load profile of the radio.

Bar indicator showing one fewer bar than expected after fitting a new pack

New Li-ion cells ship at storage voltage — typically around 3.6V — not at full charge. The THR9's bar indicator reads voltage thresholds directly, so a cell at storage voltage will display one or two bars even when the battery is unused. This is not a capacity defect. Seat the battery in the charger dock, run a full charge to completion, and the indicator will read at the correct level. Do not judge the pack's condition until after that first full charge cycle.