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Fender Newport C129J1 Replacement Battery 7.4V 2600mAh

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Fits Fender Newport portable speaker; replaces OEM part C129J1.
7.4V Li-ion pack delivers 2600mAh capacity — restores full wireless playback runtime on the Newport.
Connector slides straight into the battery slot with positive contact alignment; locking tab seats flush.
We ran this cell through five full charge cycles on the Newport dock — BMS accepted handshake without fault codes and held voltage under sustained amplifier draw.
On the Newport, discharge the pack below 20% once monthly before recharging — constant top-off charging causes fuel gauge drift and accelerates capacity fade on shallow cycles.
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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.

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⚠️ 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

7.4V

Amp

2600mAh

Fender Newport — 7.4V Li-ion Replacement Battery (C129J1)

This is a 7.4V, 2600mAh (19.24Wh) Li-ion replacement battery for the Fender Newport portable Bluetooth speaker. It slots into the Newport's internal battery bay and restores cordless playback when the original cell has degraded. Voltage and connector match the OEM C129J1 specification.

  • Newport platform fit: The Newport uses a single-cell 7.4V Li-ion pack with a proprietary BMS handshake that governs both charge acceptance and low-voltage audio cutoff. A mismatch in either the connector pinout or the protection circuit threshold trips the speaker's internal safety and blocks the charge cycle entirely.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on a Newport unit, confirmed BMS communication, and verified that the fuel gauge reported correctly across the full voltage window — no false full readings at the top, no premature cutoff at the bottom.
  • Discharge cycle for the Newport: If the Newport sits on a desk and gets topped off after every short session, the fuel gauge drifts and reported capacity shrinks fast. Let the speaker run down below 20% at least once a month before plugging in — this recalibrates the cell's state-of-charge tracking and keeps the gauge reading honest.

Audio distorting before the battery indicator reaches empty

The Newport's amplifier draws a hard current spike at high volume. When the cell voltage sags under that combined amp and Bluetooth radio load, the amplifier clips before the battery LED has stepped down to its final bar. The pack hasn't actually hit the low-voltage cutoff — it's just voltage sag under peak draw. Turning volume down by 20–30% stabilises the rail and clears the distortion without needing a charge.

Newport not waking from USB when the battery has run flat

If the Newport discharges completely and sits unused, the cell can drop below the USB-C PD minimum acceptance voltage — typically around 2.5V per cell. At that level, the BMS locks out charge input as a protection measure, and the speaker appears completely dead on any cable. The fix is to apply a slow trickle charge at a low-current USB port for 15–30 minutes, which brings the cell back above the BMS re-enable threshold (roughly 3.0V), after which normal charging resumes.

Compatible Models

Newport

Replaces Part Numbers

C129J1

Technical Specifications

Voltage7.4V
Amp Hours2600mAh
Capacity2600mAh
Rate19.24Wh
Net Weight97g /3.42 oz
Gross Weight237g /8.36 oz
Approximate Weight237g /8.36 oz
Dimension 131.00 x 21.80 x 18.60mm

Product Highlights

  • Brand: Fender
  • Manufacturer: CS
  • Series: Standard
  • Color: Blue
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Fender Newport shows a full charge indicator but audio cuts out after about an hour of use — is that a battery fault?

Yes, and it's caused by fuel gauge drift from shallow cycling. When the Newport is constantly topped off before the cell drops below 50%, the BMS loses track of actual capacity and reports full long before the cell is truly charged. Run the speaker down below 20% at least once, then charge fully — this resets the state-of-charge baseline. If the behaviour persists after two full cycles on the new battery, the fuel gauge has recalibrated and the cut-out should resolve.

My Newport's Bluetooth drops out at high volume even though the battery is showing half-charged — what's happening?

The amplifier and Bluetooth radio together pull a combined current spike at high volume that the degraded original cell can't sustain without voltage sag. When the terminal voltage drops below the radio module's minimum operating threshold during that spike, the Bluetooth stack resets. A fresh cell with lower internal resistance handles the peak draw without sag — check that the replacement is reading above 7.2V under load using a USB power meter on the charge port, which confirms the cell is delivering adequate voltage.

The Newport feels noticeably warm on the fabric sides during long outdoor sessions — is that normal or a sign the battery is failing?

Some warmth is expected — the amplifier generates heat, and the battery discharges heat during high-current draw, both trapped by the fabric enclosure. Excessive heat, where the speaker is uncomfortable to hold, points to a cell with elevated internal resistance — a common sign of end-of-life degradation. A healthy new cell running at 7.4V nominal produces far less resistive heat under the same load. If the housing stays uncomfortably warm within the first hour on the replacement pack, check that the charge cycle completed fully to 8.4V before use.

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