Airbus THR9 Replacement Battery BLN-5i 3.7V 5700mAh
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Airbus THR9 Replacement Battery BLN-5i 3.7V 5700mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
Battery Care Tips
🔹 Getting Started
Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.
🔹 Keep It Healthy
Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.
Delivery and Shipping
Delivery and Shipping
🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.
Disclaimer
Disclaimer
⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.
🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.
Airbus THR9 Replacement Battery BLN-5i 3.7V 5700mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.7V
Amp
5700mAh
Airbus THR9 Series — 3.7V Li-ion Replacement Battery (BLN-5i / BLN-6)
This is a 3.7V 5700mAh Li-ion replacement battery for the Airbus THR9 series portable radio. It fits the THR9, THR9i, THR9 C-30, and THR9 Ex. The OEM part numbers are BLN-5i and BLN-6.
- THR9 series fit — all four variants: The THR9, THR9i, THR9 C-30, and THR9 Ex share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One pack covers the full platform — no adapter or modification needed.
- Bench tested on actual hardware: We ran this pack through transmit-cycle loads on the THR9 platform. The BMS held stable under repeated PTT events and the charger dock accepted the BMS handshake without a fault LED on the first insertion.
- Contact strip check on first dock insertion: If the charger shows a fault LED when you first seat this battery, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The THR9 dock requires a clean contact cycle before it recognises a new BMS — this clears the fault in most cases without returning the unit.
Why the THR9 cuts out mid-transmission on a new BLN-5i
A new cell ships at storage voltage — typically 3.6V to 3.85V, not a full charge. When the THR9 keys up to transmit, current draw spikes sharply. If the cell voltage at that moment sits below the BMS transmit threshold, the BMS trips the output to protect the cell. This looks like a mid-transmission dropout but it is not a faulty pack. Charge the battery fully before first operational use and the BMS will hold through normal PTT events.
Bar indicator showing one fewer bar than expected after fitting the BLN-5i
The THR9 reads battery level using voltage-threshold steps — each bar corresponds to a voltage band. A new pack at storage voltage sits in the second or third band, so the indicator shows one or two bars short of full on first power-up. This is not a capacity defect. Put the pack through a full charge cycle in the THR9 dock and let it reach 4.2V before checking the bar indicator again.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Airbus
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-ion
- Battery Type: Li-ion
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My THR9 drops to low transmit power mid-shift even though the battery showed full at the start — what causes this?
Sustained RF output pulls more current than standby, and if the cell has accumulated charge cycles, internal impedance rises. Under that load, voltage sags below the THR9's full-power TX threshold, so the radio steps down output to protect the circuit — the bar indicator may still show two or three bars because it reads resting voltage, not load voltage. This is a cell impedance issue, not a firmware or radio fault. Fit a fresh pack and the TX power will hold across the shift.
The THR9 charger dock never advances to green after inserting the new BLN-6 — it just stays on amber or blinks continuously. How do I fix this?
A pack that has been in storage for several months can sit below the dock's acceptance voltage floor — typically around 3.0V. The dock sees the cell as potentially over-discharged and refuses to enter the normal charge cycle. Remove the battery, wipe the gold contacts on both the pack and the dock with a dry cloth, and reseat firmly. If the dock still will not accept it, place the pack in any compatible THR9-series radio and power the radio on for 60 seconds — this draws a small current and raises the cell voltage just enough for the dock to recognise it as a recoverable pack.
The THR9 powers on fine but cuts out completely the moment I press PTT — new battery, first use. What's happening?
This is a BMS overcurrent trip triggered by the transmit current spike. At storage voltage the cell's available current headroom is narrow, and the BMS cuts output the instant TX load exceeds its threshold. It is not a radio fault and not a defective pack. Charge the BLN-5i fully to 4.2V before first use, then retry — the BMS will hold through the PTT spike at full charge.
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