{"product_id":"att-4188c-replacement-battery-385v-2850mah-li-ion","title":"AT\u0026T 4188C Replacement Battery 3.85V 2850mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAT\u0026amp;T 4188C — 3.85V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.85V, 2850mAh Li-ion replacement battery for the AT\u0026amp;T 4188C smartphone. It fits the internal battery slot of the 4188C and restores the phone's ability to power calls, messaging, and apps. Voltage and capacity match the original cell specification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eAT\u0026amp;T 4188C compatibility:\u003c\/strong\u003e\n    The 4188C uses a 3.85V nominal cell with a charge cutoff near 4.35V. This replacement matches that voltage rail and connector pinout so the charge IC and BMS handshake proceed without fault codes.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through charge and discharge on the 4188C platform. The BMS accepted the cell without triggering a charge-stop fault, and the fuel gauge IC began tracking state-of-charge from the first full cycle.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installing this cell, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the 4188C reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe 4188C tracks charge using a fuel gauge IC that stores a learned discharge curve from the previous cell. When you install a new cell, that stored curve no longer matches the actual chemistry. The gauge reads state-of-charge against the old curve, so percentage on screen drifts from real capacity. One full discharge to shutdown followed by a full charge to 100% resets the coulomb counter and re-anchors the gauge to the new cell.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the cell voltage drops sharply under load — typically during a cellular data burst or screen-on event — and hits the BMS low-voltage cutoff before the gauge reaches 0%. The fuel gauge shows 20–30% but the cell cannot sustain voltage under that current draw. It is a calibration gap, not a defective cell. Run two full discharge-charge cycles and the gauge will anchor closer to the real voltage cliff, usually around 3.4–3.5V under load.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391861882970,"sku":"BWCS-OTB502SL-1","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391861915738,"sku":"BWCS-OTB502SL-2","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391861948506,"sku":"BWCS-OTB502SL-3","price":29.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-OTB502SL-1.webp?v=1779142388","url":"https:\/\/batteryweb.com\/products\/att-4188c-replacement-battery-385v-2850mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}