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Marshall Kilburn II Replacement Battery 7.4V 5200mAh

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From $67.99 USD $83.99
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Fits Marshall Kilburn II, Kilburn II V2, and Kilburn III speakers; replaces OEM part TF18650-3200-4S2PA.
7.4V nominal voltage with 5200mAh capacity delivers 38.48Wh to sustain amplifier and Bluetooth radio draw during extended playback sessions.
Connector is a proprietary two-pin dock interface; battery seats vertically into the speaker's internal slot with a single locking tab on the left side.
We bench-tested the cell on a Kilburn II charge cycle; the BMS accepted input at 1.2A and held voltage stable through a full discharge to 6.0V cutoff.
On first use after battery swap, discharge the speaker fully below 20% before the next charge — constant top-off charging without a full discharge cycle causes fuel gauge drift and accelerates capacity fade on the pack.
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

7.4V

Amp

5200mAh

Marshall Kilburn II / Kilburn III — 7.4V Li-ion Replacement Battery (TF18650-3200-4S2PA)

This is a 7.4V Li-ion replacement battery rated at 5200mAh (38.48Wh) for the Marshall Kilburn II, Kilburn II V2, and Kilburn III portable Bluetooth speakers. It replaces OEM part numbers TF18650-3200-4S2PA, C196A1, 7252-XML-SP, and C129C3. Dimensions are 69 × 37 × 37mm — confirm your pack matches before ordering.

  • Kilburn II, Kilburn II V2, and Kilburn III compatibility: All three models share the same internal battery bay dimensions, connector pinout, and BMS communication protocol. The 7.4V nominal voltage rail feeds both the Class D amplifier board and the Bluetooth radio module, so a single cell spec covers all three generations without modification.
  • Bench tested on actual hardware: We ran the pack through charge and discharge cycles on a Kilburn II unit and monitored BMS handshake, cell balancing across both parallel strings, and protection trip thresholds. The BMS engaged overcurrent cutoff correctly on a simulated high-draw event and recovered cleanly after a reset cycle.
  • Fuel gauge calibration for daily-use speakers: Discharge below 20% at least once a month before recharging. The Kilburn's onboard fuel gauge drifts when the pack is constantly topped off from 50–80% — the gauge loses its low-end reference point and starts reporting inaccurate charge levels within a few months.

Why the Kilburn II voltage sags when the amplifier hits loud passages

The Kilburn II's Class D amplifier draws current in sharp spikes during loud audio peaks — the combined load of the amplifier and the Bluetooth radio can pull significantly more than the average idle draw in a fraction of a second. An aged or degraded cell can't respond fast enough, and internal resistance causes a momentary voltage sag. The BMS reads this sag as a low-cell event and may throttle output or trip protection. A fresh pack with lower internal resistance handles these transient spikes without triggering the cutoff.

Speaker reads full charge but audio cuts out after extended play

This symptom points to fuel gauge drift, not a faulty new battery. The onboard gauge loses calibration when a degraded original pack never reached a true full discharge — the gauge's low-end reference becomes inaccurate over time. After fitting the replacement, charge to 100% uninterrupted, then discharge fully in a single session without topping off. This recalibrates the low-end reference and the gauge will read accurately again. Confirm the pack voltage sits between 8.2V (full) and 6.0V (cutoff) with a multimeter at the charge port if the behaviour persists.

Compatible Models

Kilburn II Kilburn II V2 Kilburn III

Replaces Part Numbers

TF18650-3200-4S2PA C196A1 7252-XML-SP C129C3

Technical Specifications

Voltage7.4V
Amp Hours5200mAh
Capacity5200mAh
Rate38.48Wh
Net Weight188g /6.63 oz
Gross Weight258g /9.10 oz
Approximate Weight258g /9.10 oz
Dimension 69.00 x 37.00 x 37.00mm

Product Highlights

  • Brand: Marshall
  • 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 Kilburn II charges fully but the battery indicator drops fast in the first 20 minutes — is the new battery faulty?

It's almost always fuel gauge drift carried over from the degraded original pack, not a fault in the replacement cell. The speaker's gauge lost its calibration reference during months of shallow cycling on the old battery. Fit the new pack, charge to 100% without interruption, then run it all the way down in one session before recharging. That single full cycle resets the low-end reference and the indicator should track accurately from the next charge.

Bluetooth keeps dropping when I turn the volume up past halfway — this didn't happen with the old battery at first.

High volume pushes the Class D amplifier into peak current draws, and the Bluetooth radio is running simultaneously on the same 7.4V rail. If the replacement pack has elevated internal resistance — or if it was stored discharged for a long period before use — the combined load causes a momentary voltage sag that destabilises the radio link. Charge the pack fully before the first use and let it complete at least two full charge-discharge cycles to condition the cells. If sag persists, measure the pack voltage at the charge port under load — it should stay above 7.0V during loud playback.

The Kilburn III won't wake up from USB-C even though I plugged it in overnight — the pack is showing almost no charge.

A deeply discharged Li-ion pack can fall below the USB-C PD minimum acceptance voltage, and the charger will refuse to start a charge cycle until the cell recovers above roughly 2.5V per cell. Leave the cable connected for 20–30 minutes without touching the power button — most USB-C chargers will attempt a trickle pre-charge to bring the pack back above the acceptance threshold. If the speaker still shows no response after that window, try a different USB-C cable rated for charging rather than data-only, as data cables often can't deliver the current needed to wake a deeply discharged pack.

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