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Fossil Launches LTE Smartwatch Replacement Battery 3.8V 300mAh

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New arrival
From $38.99 USD $47.99
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Fits Fossil Launches LTE smartwatch; replaces OEM part APP00277.
3.8V, 300mAh lithium-polymer cell powers display, processor, LTE connectivity, and sensors.
Connector seats into the proprietary pad; no locking tab; flat orientation required.
Bench test shows BMS accepted charge curve on first insertion; voltage held steady.
After fitting, place watch on charger immediately and charge to 100% — the fuel gauge IC cannot calibrate without a full charge cycle from near-zero after 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

3.8V

Amp

300mAh

Fossil Launches LTE — 3.8V Li-Polymer Replacement Battery (APP00277)

This 3.8V, 300mAh Li-Polymer cell replaces the original battery in the Fossil Launches LTE smartwatch. It restores power to the display, processor, BLE radio, heart rate sensor, and LTE modem. Dimensions are 28.80 × 23.70 × 3.80mm — match these before fitting.

  • Launches LTE platform fit: The Launches LTE draws across multiple subsystems simultaneously — LTE modem, optical HR sensor, and Wear OS processor share a single cell. This cell matches the voltage rail and connector footprint that platform requires.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the Launches LTE platform. The BMS accepted the cell without fault flags, and the fuel gauge IC registered charge state correctly after a full initial cycle from near-zero.
  • Fuel gauge recalibration after swap: Place the watch on its charger immediately after fitting this cell and charge to 100% before use. The fuel gauge IC on Wear OS platforms cannot set an accurate reference point without one full charge cycle from near-zero following a cell change.

LTE modem current spikes and what they do to a small cell

The LTE radio in the Launches LTE pulls short, sharp current spikes when it registers on a network or syncs data — more than the HR sensor or display draw individually. A worn original cell sags in voltage during these spikes, triggering low-voltage shutoff before the display reads empty. A fresh 300mAh cell at full specification handles these transient loads without the same voltage sag. If you still see unexpected shutoffs after fitting this cell, check that LTE is not set to continuous background sync.

Watch not pairing with phone after battery replacement

Removing the original cell clears the active BLE session between the watch and its paired phone. The phone retains the old pairing record, but the watch boots with no matching session — so the connection never re-establishes on its own. Open the Fossil app on your phone, remove the existing watch entry, then run a fresh pair from the watch's Bluetooth settings. Once paired, the watch reconnects to Google account sync and notification relay normally.

Compatible Models

Launches LTE

Replaces Part Numbers

APP00277

Technical Specifications

Voltage3.8V
Amp Hours300mAh
Capacity300mAh
Rate1.14Wh
Net Weight6g /0.21 oz
Gross Weight31g /1.09 oz
Approximate Weight31g /1.09 oz
Dimension 28.80 x 23.70 x 3.80mm

Product Highlights

  • Brand: Fossil
  • 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 Fossil Launches LTE shows 0% and won't turn on right after I put the new battery in — did I get a dead cell?

The fuel gauge IC loses its reference voltage when you remove the original cell, so it reads the new cell as empty even if it arrived partially charged. Place the watch straight onto its charger and leave it until it reaches 100% without interruption. That full charge cycle from near-zero resets the IC's reference point. After that first complete charge, the percentage readout will track correctly.

New battery fitted, but the watch is draining completely within a day — my old battery lasted longer even when it was worn out.

Always-on display combined with continuous heart rate monitoring and active LTE background sync is a high combined draw for a 300mAh cell. Check your watch settings — if always-on display and continuous HR are both enabled alongside LTE, that combination will drain any cell in this capacity class in roughly a single day. Disable always-on display or set HR monitoring to periodic rather than continuous. That change alone significantly reduces the load on the cell.

The magnetic charger clicks into place but the watch stays at 0% and shows no charging indicator — charge contacts issue?

Reassembly can shift the charge contact pads slightly out of alignment, so the magnet seats but the electrical connection is weak or absent. Remove the watch from the charger, inspect the four contact pins on the watch back for any debris or adhesive residue from the swap, then re-seat it on the charger at a slightly different rotational angle. If the charging indicator appears, leave it to reach 100% before use — a confirmed charge animation at the 30-second mark means contact is good.

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