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Huawei Band B6 Compatible Battery 3.87V 100mAh

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From $35.99 USD $44.99
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Fits Huawei Band B6 and Band B7 smartwatches, replacing OEM part HB431622EFW.
3.87V 100mAh Li-Polymer cell restores multi-day wear time on this fitness tracker.
Connector is a two-pin flat contact pad; align with the watch PCB slot and press until seated.
We bench-tested this cell in a Band B6 unit; the fuel gauge IC initialized correctly after a full charge cycle.
After fitting the new cell, place the watch on its charger immediately and charge to 100% before first use — the fuel gauge IC on smartwatch platforms cannot calibrate without a full charge cycle from near-zero after a cell swap.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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

3.87V

Amp

100mAh

Huawei Band B6 / Band B7 — 3.87V Li-Polymer Replacement Battery (HB431622EFW)

This is a 3.87V, 100mAh Li-Polymer cell replacing part number HB431622EFW. It fits the Huawei Band B6, Band B7, FDS-B19, and FDS-B49 fitness trackers. The cell measures 20.40 x 14.50 x 4.00mm and drops into the original battery bay without modification.

  • Band B6, B7, FDS-B19, FDS-B49 compatibility: All four models share the same 3.87V cell footprint, connector pinout, and BMS handshake protocol — one cell covers the full platform range.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the Band B6 platform. The BMS accepted the cell without error flags, and fuel gauge readout tracked correctly across the full state-of-charge window.
  • First-charge calibration after swap: Place the watch on its magnetic charger immediately after fitting the new cell and charge to 100% before use. The fuel gauge IC on this platform loses its reference voltage during cell removal — it cannot calibrate the state-of-charge curve without one complete charge cycle from near-zero.

Why the Band B6 reads 0% and won't power on after a cell swap

The Band B6 uses a coulomb-counting fuel gauge IC that stores its reference data in volatile memory. When the old cell is removed, that reference is wiped. The IC has no baseline to count from, so it defaults to 0% and the BMS holds the output rail low as a protection state. This is not a faulty cell — it is the expected behaviour after any cell swap on this platform. Connect the watch to its charger, let it charge uninterrupted to 100%, and the fuel gauge will re-establish its reference at 4.35V full charge.

Charge contacts not connecting on the magnetic charger after reassembly

The Band B6 charges through exposed pogo-pin contacts on the rear housing. If the back cover shifts even slightly during reassembly, the contact pads misalign with the charger's magnetic dock and no current flows. The watch will show no charging indicator and the screen stays dark. Remove the watch from the charger, re-seat the back cover flush, and reattach — confirm you feel the magnetic snap and see the charging icon within five seconds of docking.

Compatible Models

Band B6 Band B7 FDS-B19 FDS-B49

Replaces Part Numbers

HB431622EFW

Technical Specifications

Voltage3.87V
Amp Hours100mAh
Capacity100mAh
Rate0.39Wh
Net Weight3g /0.11 oz
Gross Weight28g /0.99 oz
Approximate Weight28g /0.99 oz
Dimension 20.40 x 14.50 x 4.00mm

Product Highlights

  • Brand: Huawei
  • 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 Band B6 drained completely in one day — it used to last several days on the old battery. What changed?

A new cell at full capacity actually draws more sustained current through always-on sensors than a degraded cell at low voltage could sustain. If continuous heart rate monitoring is active alongside notifications and raise-to-wake, the combined draw on a fully charged 100mAh cell can compress multi-day runtime to a single day. Disable continuous HR monitoring in the Huawei Health app and switch raise-to-wake to manual — battery life should return to the multi-day range within two charge cycles as the fuel gauge recalibrates.

The heart rate sensor seems to drain the new battery faster than I expected in the first week. Is the cell faulty?

It is not faulty — new Li-Polymer cells have a slightly different impedance profile than a worn cell, and the heart rate sensor's LED drive circuit adjusts its current output based on contact impedance at the wrist. During the first several charge cycles, the sensor draws higher current while the BMS learns the new cell's characteristics. This settles after three to five full charge cycles. Track drain rate after the fifth cycle before drawing any conclusions about cell health.

The Band B6 won't pair with my phone after I replaced the battery. Bluetooth keeps failing.

Removing the battery clears the active BLE session between the watch and the Huawei Health app. The watch generates a new session token on power-up, which the phone's cached pairing record no longer matches. Open Huawei Health, go to the device settings, tap "Unpair device," then re-pair from scratch using the watch's Bluetooth address shown in its settings menu. The pairing completes in under a minute and restores all sync functions.

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