{"product_id":"apple-watch-series-s6-40mm-replacement-battery-385v-260mah-li-polymer","title":"Apple Watch Series S6 40mm Replacement Battery 3.85V 260mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eApple Watch Series S6 40mm — 3.85V Li-Polymer Replacement Battery (A2345)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.85V, 260mAh Li-Polymer cell is the direct replacement for the Apple Watch Series S6 40mm. It fits the 40mm case only — not the 44mm variant. Swap it when the original cell no longer holds charge through a full day of normal use.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eS6 40mm cell dimensions:\u003c\/strong\u003e\n    The A2345 cell measures 25.30 × 18.50 × 4.60mm. The 44mm S6 uses a physically larger cell with a different part number. Fitting the wrong size risks pressure damage to the display and incorrect BMS handshake with the S6's power management IC.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell through charge-discharge cycles on S6 hardware. The BMS accepted the cell without error flags, the fuel gauge recalibrated after a full charge from near-zero, and health reporting in watchOS stabilised within two full cycles.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003ePost-swap charge protocol:\u003c\/strong\u003e\n    After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The S6 fuel gauge IC loses its reference point when the cell is disconnected. Without a full charge cycle from near-zero, the percentage display will read inaccurately for days.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the S6 fuel gauge reads wrong after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eApple Watch uses a coulomb-counter IC that tracks charge state relative to a known baseline. Removing the cell clears that baseline entirely. When a new cell is fitted, the IC has no reference, so it estimates — often badly. A full charge to 100% from a low state gives the IC a fixed endpoint to anchor its model. Until that anchor exists, watchOS will show erratic percentages that do not reflect actual capacity.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWatch not pairing with iPhone after battery replacement\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eRemoving the battery cuts power to the BLE radio mid-session. The iPhone retains the old session key, but the watch boots with no active session — the two sides are out of sync. This is not a hardware fault. On the iPhone, open the Watch app, go to General → Reset, and select \"Erase Apple Watch Content and Settings,\" then re-pair. The watch will reconnect cleanly and restore from backup.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43416160075866,"sku":"BWCS-IPW640SH-1","price":38.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43416160108634,"sku":"BWCS-IPW640SH-2","price":45.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43416160141402,"sku":"BWCS-IPW640SH-3","price":49.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-IPW640SH-1.webp?v=1779760522","url":"https:\/\/batteryweb.com\/products\/apple-watch-series-s6-40mm-replacement-battery-385v-260mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}