{"product_id":"fairphone-fairphone-5-replacement-battery-385v-4000mah-li-polymer","title":"Fairphone 5 F5AC1 Replacement Battery 3.85V 4000mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eFairphone Fairphone 5 — 3.85V Li-Polymer Replacement Battery (F5AC1)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.85V, 4000mAh Li-Polymer replacement battery for the Fairphone 5 smartphone. It fits the Fairphone 5 directly, matching the OEM part number F5AC1. Voltage and capacity are identical to the factory cell this battery replaces.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eFairphone 5 cell compatibility:\u003c\/strong\u003e\n    The Fairphone 5 uses a user-replaceable cell format with a dedicated BMS handshake tied to the F5AC1 part number. The connector orientation and contact pitch are specific to this model — cells from earlier Fairphone generations do not share this footprint.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell in a Fairphone 5 unit and confirmed the BMS accepted the cell on first power-on, reported state-of-charge correctly, and passed USB-PD negotiation without triggering a charge fault.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    Disable fast charging for the first complete discharge-charge cycle after installation. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state, which can cause erratic percentage readings or early shutdowns.\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 a replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff issue, not a capacity problem. Under high-draw conditions — active modem, GPS, and screen at full brightness simultaneously — a new cell that hasn't been calibrated can sag below the BMS cutoff threshold while the fuel gauge still reads 20–30%. The phone cuts out because actual cell voltage drops under load even though the reported percentage looks safe. One full slow-charge cycle resets the coulomb counter and gives the fuel gauge IC an accurate baseline. After calibration, the reported percentage tracks actual voltage far more closely.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eUSB-PD fast charge not negotiating after cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eOn the first cycle after a cell replacement, the Fairphone 5 charge IC may default to standard 5V charging rather than negotiating a higher USB-PD voltage tier. This happens because the BMS treats an unknown state-of-charge as a safety condition and limits the initial charge rate. Plug in and leave the phone charging for at least 20 minutes from a cold state — the IC will renegotiate once the cell voltage rises above approximately 3.6V. Fast charging should resume normally on subsequent cycles once the BMS registers a completed cycle.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391769739354,"sku":"BWCS-FPE500SL-1","price":43.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391769772122,"sku":"BWCS-FPE500SL-2","price":51.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391769804890,"sku":"BWCS-FPE500SL-3","price":56.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-FPE500SL_1.webp?v=1779141870","url":"https:\/\/batteryweb.com\/products\/fairphone-fairphone-5-replacement-battery-385v-4000mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}