{"product_id":"redmi-9s-replacement-battery-385v-4800mah-li-polymer","title":"Redmi 9s BN55 Replacement Battery 3.85V 4800mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eRedmi 9s — 3.85V Li-Polymer Replacement Battery (BN55)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.85V, 4800mAh Li-Polymer replacement battery for the Xiaomi Redmi 9s smartphone. It carries OEM part number BN55 and fits the Redmi 9s directly. Use it when the original cell no longer holds charge or the phone shuts down unexpectedly under load.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eRedmi 9s fit:\u003c\/strong\u003e\n    The BN55 cell was released as the sole battery configuration for the Redmi 9s. The connector, BMS handshake voltage, and physical footprint — 89.10 × 64.80 × 4.65mm — match the original bay 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 discharge and charge sequences on a Redmi 9s. The BMS accepted charge correctly, and the fuel gauge IC tracked state-of-charge without triggering erratic readings or unexpected cutoffs.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fast charge protocol:\u003c\/strong\u003e\n    On first use after installation, disable fast charging and complete one full discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes into an uncalibrated state.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the Redmi 9s after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens because the fuel gauge IC is still using the discharge curve it mapped for the old, degraded cell. When the new cell hits a voltage point the IC wasn't expecting, it interprets it as critically low and commands a shutdown — even though charge remains. The fix is one complete discharge-charge cycle with fast charging disabled. After that cycle, the coulomb counter re-maps against the new cell and percentage readings stabilise.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eRedmi 9s not powering on after the BN55 sat in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-Polymer cells that self-discharge in storage can drop below 2.5V per cell, triggering a BMS lockout that blocks normal charging. The phone will show no sign of life when plugged in. Connect to a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing the power button. Once the BMS detects sufficient voltage recovery, the charge IC re-engages and the phone will boot normally.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391947866202,"sku":"BWCS-MUR910SL-1","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391947898970,"sku":"BWCS-MUR910SL-2","price":34.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391947931738,"sku":"BWCS-MUR910SL-3","price":37.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-MUR910SL-1.webp?v=1779142720","url":"https:\/\/batteryweb.com\/products\/redmi-9s-replacement-battery-385v-4800mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}