{"product_id":"vivo-y71-replacement-battery-385v-3300mah-li-polymer","title":"Vivo Y71 Replacement Battery BK-B-E1 3.85V 3300mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eVivo Y71 Series — 3.85V Li-Polymer Replacement Battery (BK-B-E1)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3300mAh (12.71Wh) Li-Polymer cell rated at 3.85V, built to replace the original BK-B-E1 battery in the Vivo Y71. It fits the standard Y71, Y71 Dual SIM, and Y71 Dual SIM TD-LTE variants. Swap it in when the original cell can no longer hold a usable charge through a normal day.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eY71 variant coverage:\u003c\/strong\u003e\n    The standard Y71, Dual SIM, and Dual SIM TD-LTE share the same physical battery bay dimensions, voltage rail, and BMS connector pinout — one cell covers all three without modification.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through full charge and discharge on a Y71 unit. The BMS accepted the charge handshake without fault codes, and the protection circuit tripped correctly at the low-voltage cutoff threshold.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins against an uncalibrated reference.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Y71 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Y71 uses a coulomb counter IC that builds its charge model against the original cell's discharge curve over hundreds of cycles. When a new cell goes in, that learned curve no longer matches the actual cell chemistry and capacity. The gauge then reports percentages based on stale data — often reading 100% early into a charge or dropping suddenly under moderate load. One full discharge below 10% followed by a complete uninterrupted charge resets the counter's reference points against the new cell.\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 cell voltage drops sharply under screen or modem load — a voltage cliff the fuel gauge did not predict because it was still using the old cell's model. The phone's protection threshold triggers a shutdown before the displayed percentage reaches zero. It is not a faulty cell — it is a calibration gap. After two or three full discharge-charge cycles, the gauge tightens its curve and the shutdowns stop. If they persist past three cycles, check that resting cell voltage sits at or above 3.85V with a multimeter after a full charge.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43392023167066,"sku":"BWCS-BYX710SL-1","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43392023199834,"sku":"BWCS-BYX710SL-2","price":28.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43392023232602,"sku":"BWCS-BYX710SL-3","price":31.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-BYX710SL-1.webp?v=1779142944","url":"https:\/\/batteryweb.com\/products\/vivo-y71-replacement-battery-385v-3300mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}