LEXIN LX-B4FM Wireless Headset Replacement Battery 3.7V 800mAh
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LEXIN LX-B4FM Wireless Headset Replacement Battery 3.7V 800mAh - 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.
LEXIN LX-B4FM Wireless Headset Replacement Battery 3.7V 800mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.7V
Amp
800mAh
LEXIN LX-B4FM / FT4 Pro — 3.7V Li-Polymer Replacement Battery (AHB802540)
This is a 3.7V 800mAh Li-Polymer cell that replaces the original AHB802540 pack in the LEXIN LX-B4FM and FT4 Pro motorcycle Bluetooth headsets. It fits directly into both models, which share the same battery bay dimensions and BMS handshake protocol. Capacity is 800mAh (2.96Wh), matching the factory specification.
- LX-B4FM and FT4 Pro compatibility: Both models run the same 3.7V single-cell architecture with an identical connector and BMS communication line. One replacement cell covers both units without any wiring changes.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the LX-B4FM platform. The BMS accepted the cell without fault codes, and protection thresholds tripped correctly at low-voltage cutoff.
- First-cycle charging on the headset: After fitting this battery, seat the headset in its charging cradle and let it complete one full, uninterrupted charge before use. The LX-B4FM's firmware logs the new cell during that first cycle — skip it and the talk-time indicator will read inaccurately for the first several sessions.
Why the LX-B4FM cuts out mid-call on a fresh battery
The LX-B4FM combines Bluetooth audio and intercom radio draw simultaneously during a call. That combined current spike can briefly pull cell voltage below the BMS cutoff threshold — especially on a new cell that hasn't completed its first full conditioning cycle. The BMS reads the sag as an undervoltage event and shuts the unit down to protect the cell. This typically resolves after three to five full charge-discharge cycles, once the cell's internal resistance settles to its operating baseline.
Headset shows full charge but cuts off after a few minutes of use
A replacement cell shipped at storage voltage — roughly 3.6–3.7V — can fool the headset's charge indicator into displaying a full bar. The cell isn't actually fully charged; it's just resting above the empty threshold. Seat the headset in the cradle, wait for the indicator to cycle through to a confirmed full charge, then disconnect. If the issue persists after two full cycles, check that the cradle contacts are clean and making solid connection with the headset pins.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: LEXIN
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-Polymer
- Battery Type: Li-Polymer
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My LEXIN LX-B4FM keeps dropping out mid-intercom session — is this the battery?
Most likely yes, if the original cell has degraded. The LX-B4FM draws current from both the Bluetooth radio and the intercom channel at the same time, and a worn cell can't sustain that combined load without its voltage sagging below the BMS cutoff. A new AHB802540 cell resolves this once it's been through three to five full charge cycles to condition the cell. Run the first cycle completely — full charge, then use until the headset powers off naturally.
The charging cradle shows a solid charge light but the headset's talk time is noticeably short for the first few uses — what's happening?
A new Li-Polymer cell doesn't deliver full rated capacity until it's been cycled a few times. The AHB802540 typically reaches its 800mAh rated capacity between cycles three and five. The cradle light reflects charge voltage, not cell capacity — so the indicator goes green on schedule even when the cell is still conditioning. Give it five full charge-discharge cycles before judging talk time.
The LX-B4FM headset feels noticeably warm during long rides — is that normal with a new battery?
Some warmth is expected. The LX-B4FM runs Bluetooth, intercom, and FM radio functions inside a compact housing with limited airflow, and sustained draw through a small Li-Polymer cell generates heat. If the unit is warm but not hot to the touch and powers on normally, that's within normal operating range. If it's too hot to hold comfortably, check that the battery contacts are seated flush — a partial connection creates resistance and excess heat at the terminal.
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