{"product_id":"tcl-q3-replacement-battery-37v-800mah-li-ion","title":"TCL Q3 OT-BY40 Replacement Battery 3.7V 800mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eTCL Q3 \/ I802 \/ E59 — 3.7V Li-ion Replacement Battery (OT-BY40)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 800mAh Li-ion replacement cell for the TCL Q3, I802, and E59 smartphones. It replaces OEM part OT-BY40 and TB-4X. Swap it in when the original cell no longer holds a usable charge or fails to power the device through a normal day.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eQ3, I802, and E59 compatibility:\u003c\/strong\u003e\n    These three models share the same battery bay dimensions, connector pinout, and charge IC protocol. The OT-BY40 footprint — 53.30 × 33.80 × 4.50mm — fits all three without modification.\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 cycles on the Q3 platform. The BMS accepted the full charge cycle, voltage held steady under screen-on and modem loads, and no spurious shutdowns occurred above 10% state of charge.\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 allows the fuel gauge IC to map its coulomb counter against the new cell's actual 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 TCL Q3 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe Q3 uses a fuel gauge IC that builds its charge model from accumulated coulomb-counting data on the original cell. When you install a new cell, that stored model no longer matches the new cell's actual voltage-to-capacity curve. The phone pulls percentage readings from stale calibration data until it runs a full cycle. One complete discharge to auto-shutdown followed by an uninterrupted charge to 100% resets the calibration. After that cycle, the percentage readout tracks the new cell accurately.\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 fuel gauge IC hasn't finished recalibrating and the cell voltage drops below the modem or display's minimum operating threshold before the reported percentage reaches zero. The phone cuts out not because the cell is defective, but because the voltage sags under peak load at a state of charge the gauge hasn't correctly mapped yet. Let the phone discharge fully to auto-shutdown — do not force-restart mid-cycle. After two full discharge-charge cycles, the coulomb counter aligns to the new cell curve and the early shutdowns stop.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405134233690,"sku":"BWCS-OT800SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405134266458,"sku":"BWCS-OT800SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405134299226,"sku":"BWCS-OT800SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-OT800SL-1.webp?v=1779370279","url":"https:\/\/batteryweb.com\/products\/tcl-q3-replacement-battery-37v-800mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}