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FitBit Charge 5 Compatible Battery 3.87V 65mAh LSS271617

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Sale priceFrom $26.99 USD Regular price $33.99
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Fits FitBit Charge 5 smartwatch, replaces OEM part LSS271617.
3.87V, 65mAh lithium-polymer cell powers display, heart rate sensor, and activity tracking continuously.
Connector is soldered directly to watch circuit board; no external plug or locking tab.
We bench-tested this cell in the Charge 5 platform; BMS accepted the new pack after full charge cycle from near-zero state.
After fitting the new cell, place the watch on its magnetic charger immediately and charge to 100% before first use — the fuel gauge IC cannot calibrate without a complete charge cycle from power-off after a cell swap.

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🔹 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.

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Voltage

3.87V

Amp

65mAh

FitBit Charge 5 — 3.87V Li-Polymer Replacement Battery (LSS271617)

This is a 3.87V, 65mAh Li-Polymer cell for the FitBit Charge 5 fitness tracker. It replaces OEM part LSS271617 — the same cell that powers the AMOLED display, continuous heart rate sensor, and sleep tracking. When the original cell degrades, this swap restores full function without replacing the watch.

  • Charge 5 platform fit: The Charge 5 uses a compact Li-Polymer cell at 3.87V nominal to run its sensor array and BLE stack. This cell matches that voltage rail, the 18.30 × 15.20 × 2.60mm footprint, and the flex connector termination on the Charge 5 mainboard.
  • Bench tested on actual hardware: We ran this cell in a Charge 5 unit and confirmed the fuel gauge IC accepted the new cell, the display initialised, and heart rate tracking resumed after a full charge cycle from near-zero.
  • Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before use. The Charge 5 fuel gauge IC loses its reference point when the cell is swapped — without a full charge cycle from near-zero, it cannot recalibrate and will report inaccurate percentages.

Why the Charge 5 heart rate sensor shortens new battery life in the first week

The Charge 5 runs its optical HR sensor in continuous mode by default, pulsing green LEDs and sampling the photodiode every second. A new cell has a slightly different internal impedance than the aged cell it replaced, and the power management IC briefly draws more current while it characterises the new source. This settles within five to seven charge cycles. If drain still seems high after that point, check whether Always-On Display is active in the Fitbit app — that single setting roughly doubles display draw on this platform.

Charge 5 not pairing to phone after battery swap

Removing the cell cuts power to the BLE stack entirely, which drops the active Bluetooth session and clears the pairing state held in volatile memory. The phone still shows the watch as paired, but the watch no longer recognises the bond. Open the Fitbit app, go to the device settings, tap "Remove this device," then set the Charge 5 up again as new. The sync and notification features restore fully after re-pairing.

Compatible Models

Charge 5

Replaces Part Numbers

LSS271617

Technical Specifications

Voltage3.87V
Amp Hours65mAh
Capacity65mAh
Rate0.25Wh
Net Weight1.5g /0.05 oz
Gross Weight26.5g /0.93 oz
Approximate Weight26.5g /0.93 oz
Dimension 18.30 x 15.20 x 2.60mm

Product Highlights

  • Brand: FitBit
  • 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 Charge 5 shows 0% and won't turn on straight after I replaced the battery — did I get a dead cell?

The cell is almost certainly fine. The fuel gauge IC on the Charge 5 loses its voltage reference when the cell is disconnected, and it defaults to 0% when it cannot read a calibrated state of charge. Place the watch on its magnetic charger immediately and leave it until the app reports 100% — do not try to power it on mid-charge. Once that full cycle completes from near-zero, the IC recalibrates and the watch boots normally.

The magnetic charger doesn't seem to be charging the watch after I reassembled it — the charging animation never appears.

The most likely cause is the charge contacts on the watch back shifting slightly during reassembly, breaking the magnetic alignment with the charger puck. Remove the charger, wipe both the watch contacts and the puck pins with a dry cloth, then re-seat the charger and confirm the magnet snaps flush. If the animation still does not appear, check that the flex connector for the new cell is fully pressed down on the mainboard — a partial connection can prevent the charging circuit from activating.

Battery on my Charge 5 is draining in a single day now — it used to last several days.

On a 65mAh cell, the Always-On Display and continuous heart rate monitoring together account for the majority of draw on this platform. Open the Fitbit app, go to your Charge 5 settings, and turn off Always-On Display first — that alone typically restores multi-day life. If drain remains heavy after five full charge cycles, check whether any third-party clock faces are running background sensor polls, as some query the HR sensor every 30 seconds regardless of wrist activity.

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