{"product_id":"t-king-k1391-replacement-battery-37v-2000mah-li-ion","title":"T-KING K1391 Replacement Battery 3.7V 2000mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eT-KING K1391 — 3.7V Li-ion Replacement Battery (K1391)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 2000mAh Li-ion replacement battery for the T-KING K1391 smartphone. It fits directly into K1391 devices where the original cell has degraded and can no longer hold a working charge. Capacity is 2000mAh (7.4Wh) — matching the factory specification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eK1391 platform fitment:\u003c\/strong\u003e\n    The K1391 cell uses a specific connector pinout and physical footprint — 70.00 x 59.90 x 4.40mm — that matches the T-KING K1391 chassis. The BMS communicates over the same data line as the OEM cell, so the phone's charge IC accepts it without rejection flags.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through charge and discharge on the bench, monitoring BMS handshake behaviour and cutoff thresholds. The protection circuit triggers correctly at the low-voltage floor, and the charge IC accepted the cell without error on the second cycle after fuel gauge recalibration.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fast charge behaviour:\u003c\/strong\u003e\n    After installation, disable fast charging for the first full discharge-charge cycle. The fuel gauge IC on the K1391 is calibrated to the old cell's discharge curve. Running a slow first cycle lets the coulomb counter reset against the new cell before fast charge current is applied to an uncalibrated gauge.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the K1391 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe K1391's fuel gauge IC builds its capacity model from repeated charge and discharge cycles on the original cell. When a new cell goes in, the stored discharge curve no longer matches the actual cell chemistry, so the percentage readout drifts — often showing full charge until a sudden drop. One complete slow charge and full discharge cycle forces the coulomb counter to relearn the new cell's voltage-to-capacity relationship. After that cycle, percentage tracking stabilises. Do not interrupt the first cycle early.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the modem, display, or both draw a current spike that drops the cell voltage below the BMS cutoff threshold — even though the gauge still shows charge remaining. On a new cell before calibration, the fuel gauge overestimates remaining capacity at low state-of-charge. The BMS then cuts output when voltage sags under load at what looks like 20–30%. Run two full discharge cycles without interruption to let the gauge IC map the actual low-voltage cliff of the new cell. After calibration, shutdown voltage should track closer to 3.2–3.3V under load.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404231114842,"sku":"BWCS-WKS011SL-1","price":24.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404231147610,"sku":"BWCS-WKS011SL-2","price":27.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404231180378,"sku":"BWCS-WKS011SL-3","price":30.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-WKS011SL-1.webp?v=1779369465","url":"https:\/\/batteryweb.com\/products\/t-king-k1391-replacement-battery-37v-2000mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}