{"product_id":"asus-zenfone-8-replacement-battery-387v-3900mah-li-polymer","title":"C11P2003 Asus ZenFone 8 Replacement Battery 3.87V 3900mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAsus ZenFone 8 ZS590KS — 3.87V Li-Polymer Replacement Battery (C11P2003)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.87V, 3900mAh (15.09Wh) Li-Polymer cell for the Asus ZenFone 8 (ZS590KS). It replaces OEM part numbers C11P2003 and 0B200-03950000. Fit this battery when your ZenFone 8 no longer holds a charge through a normal day of use.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eZenFone 8 \/ ZS590KS fitment:\u003c\/strong\u003e\n    Both model references — ZenFone 8 and ZS590KS — share the same physical cell format, connector pinout, and BMS handshake. One replacement covers both designations.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell through charge and discharge on ZS590KS hardware. The BMS accepted the cell without fault codes, and the charge IC cycled normally through trickle, CC, and CV stages.\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 for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's actual discharge curve before high-current charging pushes into an uncalibrated register.\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 ZenFone 8 after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eA new cell has a discharge curve the fuel gauge IC has never seen before. The IC's stored curve still maps to the old, degraded cell, so the voltage-to-percentage translation is wrong. Under heavy load — 5G modem, screen at full brightness — the new cell can sag below the shutdown threshold before the gauge shows zero. One full discharge-charge cycle rewrites the coulomb counter registers and corrects this. After calibration, shutdowns below 20% stop.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eUSB-PD fast charge not triggering on the first cycle after replacement\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eAfter fitting a new cell, the charge IC sometimes defaults to standard 5V\/1A input and won't negotiate USB-PD or HyperCharge rates. This happens because the BMS initialises conservatively when it detects a cell it hasn't profiled yet. Complete one full standard charge cycle first — let the battery reach 100% and drain to below 10% naturally. On the second charge, connect your original Asus fast charger; the BMS will accept the higher voltage negotiation once the cell profile is established.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391881117786,"sku":"BWCS-AUZ590SL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391881150554,"sku":"BWCS-AUZ590SL-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391881183322,"sku":"BWCS-AUZ590SL-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-AUZ590SL-1.webp?v=1779142478","url":"https:\/\/batteryweb.com\/products\/asus-zenfone-8-replacement-battery-387v-3900mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}