{"product_id":"bea-fon-sl660-replacement-battery-37v-900mah-li-ion","title":"Bea-fon SL660 Replacement Battery 3.7V 900mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eBea-fon SL660 Series — 3.7V Li-ion Replacement Battery (SL670, SL630\/SL640)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V 900mAh Li-ion cell replaces the original battery in the Bea-fon SL660, SL652A, SL652AF, and SL670, along with four additional SL-series variants. It fits the same physical footprint at 46.47 × 39.79 × 5.33mm and connects to the stock charge IC without modification. Capacity is 3.33Wh, matching the original cell specification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eSL-series compatibility:\u003c\/strong\u003e\n    The SL652A, SL652AF, SL660, and SL670 share the same battery bay dimensions, connector pinout, and charge IC protocol. One cell revision covers the full range without wiring changes or adapter plates.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled the cell through charge and discharge on the SL660 platform. The BMS held charge termination voltage correctly, and the fuel gauge IC accepted the new cell without throwing a fault flag after the first full cycle.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration after swap:\u003c\/strong\u003e\n    On first use after installation, disable fast charging and run one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the SL660 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe SL660 uses a fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The gauge reads voltage and estimates percentage against old data, so the number on screen can be off by 10–20%. One full discharge down to auto-shutdown, followed by a complete charge to 4.2V, resets the coulomb counter and lets the gauge relearn against the new cell.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% remaining on the SL660\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff, not a software bug. Under modem or screen load, the cell voltage drops sharply at low state of charge. If the fuel gauge IC is still calibrated to the old cell, it predicts more remaining capacity than actually exists, and the phone hits the BMS undervoltage cutoff without warning. The fix is the same full recalibration cycle — discharge to shutdown, charge uninterrupted to 4.2V, then let the gauge operate normally for two more cycles before trusting the percentage readout.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43392112885850,"sku":"BWCS-BES660SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43392112918618,"sku":"BWCS-BES660SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43392112951386,"sku":"BWCS-BES660SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-BES660SL-1.webp?v=1779143847","url":"https:\/\/batteryweb.com\/products\/bea-fon-sl660-replacement-battery-37v-900mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}