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Bose SoundLink Flex 3.7V Replacement Battery 83289

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From $43.99 USD $54.99
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Fits Bose SoundLink Flex portable speaker, replaces OEM part number 83289.
3.7V and 2600mAh capacity delivers the same energy density as the original cell for full wireless playback cycles.
Connector seats into the battery compartment slot with a positive terminal contact on the speaker's circuit board.
We bench tested the cell on a SoundLink Flex at 50% volume and observed stable BMS voltage regulation across discharge cycles.
On first charge with the SoundLink Flex, allow a complete discharge to below 20% before the next top-off cycle to recalibrate the fuel gauge.
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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

3.7V

Amp

2600mAh

Bose SoundLink Flex — 3.7V Li-ion Replacement Battery (83289)

This 3.7V, 2600mAh (9.62Wh) Li-ion cell replaces the original battery in the Bose SoundLink Flex portable Bluetooth speaker. It fits OEM part number 83289 directly. If your SoundLink Flex no longer holds a charge or powers on, this cell restores the speaker to working condition.

  • SoundLink Flex platform fit: The SoundLink Flex uses a single-cell 3.7V Li-ion pack with a proprietary connector and an integrated BMS that communicates charge state to the speaker's firmware. This cell matches that voltage rail and connector so the speaker's charge indicator reports accurately after installation.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SoundLink Flex platform. The BMS handshake completed without error codes, and the charge indicator tracked correctly from 0% to 100% across multiple cycles.
  • Fuel gauge reset after swap: After fitting this cell, run the speaker down to auto-shutdown before the first recharge. Skipping this step causes the SoundLink Flex firmware to read stale capacity data from the old pack, which produces inaccurate battery percentage readings from the first charge.

Audio distorting before the battery indicator reaches empty

The SoundLink Flex amplifier draws a surge of current at high volume. When the cell approaches the end of its discharge curve, internal resistance causes voltage to sag under that load — even if the indicator still shows 10–20% remaining. The amplifier clips because it cannot sustain rail voltage, and the audio distorts before the speaker shuts down. If this happens on a new cell, run a full discharge-to-shutdown cycle and recharge to 100% to let the BMS recalibrate its capacity reading.

SoundLink Flex won't wake from USB-C after sitting unused for weeks

A deeply discharged Li-ion cell can drop below the minimum acceptance voltage for USB-C Power Delivery negotiation. When that happens, the charger sees no valid handshake and delivers no current, so the speaker appears completely dead. The fix is to connect the speaker to a basic 5V USB-A source using a USB-A to USB-C cable rather than a PD charger — this bypasses the PD negotiation and trickle-charges the cell back above the recovery threshold of approximately 3.0V per cell. Once the cell recovers, switch to the standard USB-C charger to complete the charge cycle.

Compatible Models

SoundLink Flex

Replaces Part Numbers

83289

Technical Specifications

Voltage3.7V
Amp Hours2600mAh
Capacity2600mAh
Rate9.62Wh
Net Weight51g /1.80 oz
Gross Weight76g /2.68 oz
Approximate Weight76g /2.68 oz
Dimension 66.50 x 22.50 x 21.00mm

Product Highlights

  • Brand: Bose
  • 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 SoundLink Flex battery indicator shows 50% but the speaker cuts out completely — is the new cell faulty?

The cell is almost certainly fine. This is a fuel gauge drift issue — the SoundLink Flex firmware inherited stale capacity data from the old pack and is now misreading the new cell's state of charge. Run the speaker continuously at moderate volume until it auto-shuts down from true depletion, then charge it uninterrupted to 100%. That full cycle forces the BMS to recalibrate against the new cell's actual capacity curve.

Bluetooth keeps dropping when I push the volume past halfway — why does a new battery make this worse before it gets better?

At high volume, the amplifier and Bluetooth radio draw current simultaneously, which spikes the combined load on the cell. A new cell that hasn't completed its first full conditioning cycle has slightly elevated internal resistance, causing momentary voltage sag under that combined draw. The BMS interprets the sag as a low-voltage event and throttles or resets the radio to protect the cell. Complete two full discharge-to-shutdown and recharge cycles — internal resistance drops measurably after that, and the sag under combined amp and radio load decreases.

The speaker feels noticeably warm through the fabric housing during long play sessions — is that the battery?

Both the amplifier and the discharging Li-ion cell generate heat, and the SoundLink Flex's fabric-wrapped enclosure traps it rather than venting it the way a vented plastic shell would. Some warmth is normal. If the housing becomes hot to the touch rather than warm, the speaker's thermal protection will throttle audio output before causing damage. Keep the speaker out of direct sunlight during extended play, and avoid setting it on insulating surfaces like soft furnishings — hard flat surfaces allow more heat to conduct away from the base.

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