{"product_id":"marshall-kilburn-ii-replacement-battery-74v-5200mah-li-ion","title":"Marshall Kilburn II Replacement Battery 7.4V 5200mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eMarshall Kilburn II \/ Kilburn III — 7.4V Li-ion Replacement Battery (TF18650-3200-4S2PA)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 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.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eKilburn II, Kilburn II V2, and Kilburn III compatibility:\u003c\/strong\u003e\n    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.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    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.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge calibration for daily-use speakers:\u003c\/strong\u003e\n    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.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Kilburn II voltage sags when the amplifier hits loud passages\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe 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.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSpeaker reads full charge but audio cuts out after extended play\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis 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.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43416217911386,"sku":"BWCS-MRK200SL-1","price":67.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43416217944154,"sku":"BWCS-MRK200SL-2","price":79.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43416217976922,"sku":"BWCS-MRK200SL-3","price":88.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-MRK200SL-1.webp?v=1779761020","url":"https:\/\/batteryweb.com\/products\/marshall-kilburn-ii-replacement-battery-74v-5200mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}