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Retevis RT81 Replacement Battery BL50 7.4V 2050mAh

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From $51.99 USD $63.99
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Fits Retevis RT81, RT82, RT81V, and RT50 portable radios; replaces OEM part numbers BL50 and LB-75L.
7.4V and 2050mAh capacity delivers full transmit power without voltage sag during sustained RF output.
Slide connector mates flush with the radio battery slot; locking tab seats firmly with a click.
We bench-tested this cell in an RT81 and confirmed the BMS accepted the pack on first dock insertion without fault codes.
On first insertion into the charger dock, remove the battery and wipe the contact strip with a dry cloth if a fault LED appears; reseat firmly so the dock accepts the new BMS handshake.
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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

🔹 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: 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.

Voltage

7.4V

Amp

2050mAh

Retevis RT81 / RT82 Series — 7.4V Li-ion Replacement Battery (BL50 / LB-75L)

This is a 7.4V, 2050mAh lithium-ion battery that replaces the OEM BL50 and LB-75L packs on the Retevis RT81, RT82, RT81V, and RT50. It fits the same battery cavity and uses the same contact configuration as the original. Voltage and capacity match the factory spec exactly.

  • RT81 / RT82 / RT81V / RT50 platform fit: These models share the same 7.4V battery bay, contact strip layout, and BMS handshake protocol. One pack covers all four radios — no adapter or modification needed.
  • Bench tested on actual hardware: We cycled this pack through PTT transmit loads on the RT81. The BMS handled the current spike on key-up without tripping, and the pack held voltage across sustained transmit without dropping below the radio's low-battery threshold.
  • First insertion into the RT81 charger dock: If the dock shows a fault or blinking LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The RT81 charger requires a clean contact cycle to complete the BMS handshake before it begins charging.

RT81 cuts out mid-transmission on a new BL50 pack

New lithium-ion cells ship at storage voltage — typically 3.6–3.7V per cell, not full charge. When the RT81 keys up, transmit current demand spikes sharply. If the pack is at storage voltage, that spike can pull cell voltage below the BMS overcurrent threshold and trigger a momentary cutoff, killing the transmission. This is not a faulty pack. Fully charge the battery in the dock before the first use — a complete charge cycle brings both cells to 4.2V and gives the BMS the headroom it needs to handle PTT surges cleanly.

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

The RT81 uses a voltage-threshold bar indicator — each bar corresponds to a voltage window, not a capacity percentage. A new pack at storage voltage sits in the two-bar window even though the cell is healthy. After a full charge cycle, resting voltage rises to approximately 8.3–8.4V across the pack, and the indicator moves to the correct full-charge bar level. If the indicator stays low after a full charge, check that the gold contacts on both the pack and the radio are clean — oxide buildup on the contacts causes a small voltage drop that shifts the reading down by one bar.

Compatible Models

RT81 RT82 RT81V RT50 RT8

Replaces Part Numbers

BL50 LB-75L

Technical Specifications

Voltage7.4V
Amp Hours2050mAh
Capacity2050mAh
Rate15.17Wh
Net Weight97g /3.42 oz
Gross Weight132g /4.66 oz
Approximate Weight132g /4.66 oz
Dimension 113.60 x 55.10 x 17.90mm

Product Highlights

  • Brand: Retevis
  • 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 RT81 cuts out every time I press PTT on the new battery — is the pack defective?

Almost certainly not. New Li-ion cells arrive at storage voltage, around 3.6–3.7V per cell, and the transmit current spike on PTT can pull that low enough to trip the BMS overcurrent cutoff. Charge the pack fully in the dock before using it — both cells need to reach 4.2V before the BMS has enough headroom to handle the key-up surge. If cutouts continue after a full charge, wipe the battery contact strip and the radio contacts with a dry cloth, as a dirty connection increases resistance under load.

The RT81 charger dock is blinking and won't start a charge cycle on the new pack — what's happening?

The RT81 dock runs a contact-check before accepting a pack. If the gold contact strip has any residue or isn't seated squarely, the dock reads an incomplete circuit and holds the fault blink rather than starting charge. Remove the pack, wipe the contact strip with a dry cloth, and press it firmly back into the dock until it clicks. If the fault blink still doesn't clear, the pack may be below the dock's minimum acceptance voltage — connect it to a compatible USB charger or a different RT-series dock briefly to raise the cell voltage above 3.0V per cell, then return it to the RT81 dock.

The RT81 drops to low TX power partway through a long transmission — battery or radio fault?

This is voltage sag under sustained RF output, not a radio fault. During an extended transmission, the cells can't replenish voltage as fast as the radio draws it, and pack voltage dips below the RT81's reduced-power threshold — the radio steps down output to protect the circuit. It recovers when you release PTT and voltage rebounds. If this happens consistently on a fully charged pack, check that the battery contacts are clean and making full contact, since added resistance accelerates the sag. A healthy BL50 at full charge should sustain normal TX output through typical voice transmissions without stepping down.

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