Nokia THR850 Replacement Battery BLN-4 3.7V 2000mAh
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Nokia THR850 Replacement Battery BLN-4 3.7V 2000mAh - 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.
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Disclaimer
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🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.
Nokia THR850 Replacement Battery BLN-4 3.7V 2000mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.7V
Amp
2000mAh
Nokia THR850 Series — 3.7V Li-ion Replacement Battery (BLN-4)
This is a 3.7V 2000mAh Li-ion battery for the Nokia THR850, THR880, THR880i, and THR880i Light two-way radios. It replaces OEM part numbers BLN-4 and BLN-4D. These radios run on professional land mobile networks and are common in security, construction, and hospitality operations.
- THR850 and THR880 series compatibility: All four models in this lineup share the same 3.7V battery bay, connector pinout, and BMS handshake protocol. One pack covers the full platform.
- Bench tested on actual hardware: We cycled this pack through transmit loads on the THR850 bench rig. The BMS held voltage stable under PTT current spikes and re-engaged correctly after each discharge cycle without tripping lockout.
- First insertion into the charger dock: If the dock LED shows a fault on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The THR platform requires a clean contact cycle to complete the BMS handshake before charging begins.
THR850 dropping to reduced TX power mid-shift on a new BLN-4
New Li-ion cells ship at storage voltage — typically around 3.6V — not at full charge. The THR850 monitors supply voltage continuously and steps down transmit power when the rail drops below its threshold. This is not a faulty pack. Run the battery through one full charge cycle in the dock before putting it into active use. After that first full charge, the radio will operate at rated TX power without stepping down.
Bar indicator showing one fewer bar than expected after BLN-4 swap
The THR880 series uses a simple voltage-threshold bar indicator — it reads the pack's resting voltage and maps it to bars. A new cell at storage voltage reads lower than a fully charged cell, so the indicator shows one or two bars even on a fresh pack. This is not a capacity defect. Charge the pack fully in the dock until the LED goes green, then reinsert. The indicator will show a full bar reading once the cell sits above 4.1V.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Nokia
- Manufacturer: CS
- Series: Standard
- Color: White
- Product Type: Li-ion
- Battery Type: Li-ion
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My THR850 cuts out completely when I press PTT on the new BLN-4 — what's happening?
The transmit current spike when PTT is pressed can trip the BMS overcurrent protection if the cell is at storage voltage rather than full charge. The radio draws significantly more current at the start of transmission than at idle, and a low-voltage cell cannot sustain that draw. Charge the pack fully before first use in the field. If it cuts out after a full charge, wipe the battery contacts and dock pins — a resistive contact raises apparent impedance and can trigger the same BMS response.
The charger dock LED has been blinking for two hours and never goes steady — is the pack dead?
A blinking dock LED on the THR platform usually means the pack voltage is below the dock's acceptance threshold, which happens when a cell has sat in storage for an extended period. The dock will not begin a full charge cycle until the pack clears that minimum voltage. Remove the battery, wait five minutes, and reinsert — some dock firmware will retry the BMS handshake on a fresh insertion. If the LED still blinks after two reinsertion attempts, check that the gold contact strip on the battery is clean and making firm contact with the dock pins.
The THR880i shows a full bar reading in the office but drops to one bar as soon as I start a long transmission — is this pack undersized?
This is voltage sag under sustained RF output load, not a capacity issue. During a long transmission, the radio draws continuous current from the cell, and voltage drops under that sustained load — the bar indicator tracks that real-time voltage drop. The 2000mAh BLN-4 is the correct capacity for this platform. If the sag is severe enough to drop to one bar within seconds, check that the battery contacts are seated fully and that the dock completed a full charge cycle — a partial charge will amplify the sag effect under load.
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