{"product_id":"neffos-x20-replacement-battery-385v-3900mah-li-polymer","title":"Neffos X20 Compatible Battery 3.85V 3900mAh NBL-43A4000","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eNeffos X20 \/ X20 Pro Series — 3.85V Li-Polymer Replacement Battery (NBL-43A4000)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.85V, 3900mAh Li-Polymer cell that replaces part number NBL-43A4000 in the Neffos X20, X20 Pro, TP7071, and TP9131A smartphones. The original cell degrades through charge cycles and loses the ability to hold voltage under load, cutting the phone off before the display reads zero. This replacement restores full charge capacity to the stock specification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eX20 and X20 Pro compatibility:\u003c\/strong\u003e\n    Both the X20 (TP7071) and X20 Pro (TP9131A) share the NBL-43A4000 cell footprint, voltage rail, and BMS connector pinout. Swapping between variants does not require firmware changes or connector adapters.\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 X20 platform and confirmed BMS handshake, charge acceptance, and voltage delivery under screen-on and modem-active loads. No fault flags triggered during testing.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fast charge caution:\u003c\/strong\u003e\n    After installation, disable fast charging for one full discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell, which can cause erratic percentage readings early on.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the X20 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe X20 uses a fuel gauge IC that learns a cell's discharge curve over cycles. When you install a new cell, the IC still holds the old cell's calibration data. It maps voltage readings to percentage estimates based on a worn curve, so the numbers it reports can be off by 10–20% until it relearns. One full discharge to auto-off followed by a complete charge cycle resets the coulomb counter and lets the IC build an accurate model of the new cell.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% charge on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the fuel gauge IC is still calibrated to the old cell and reads the voltage incorrectly under load. A fresh Li-Polymer cell has a steeper voltage cliff than a degraded one — under modem or screen load, voltage drops fast enough to trigger low-voltage protection before the display percentage catches up. The fix is one full calibration cycle: drain the phone until it shuts itself off, then charge uninterrupted to 100% without fast charge enabled. After that cycle, the IC recalibrates and shutdown behaviour normalises above 3.4V per cell.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391921520730,"sku":"BWCS-TPX200SL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391921553498,"sku":"BWCS-TPX200SL-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391921586266,"sku":"BWCS-TPX200SL-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-TPX200SL-1.webp?v=1779142694","url":"https:\/\/batteryweb.com\/products\/neffos-x20-replacement-battery-385v-3900mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}