{"product_id":"att-gophone-gemini-replacement-battery-37v-800mah-li-ion","title":"AT\u0026T Gophone GEMINI Compatible Battery 3.7V 800mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAT\u0026amp;T Gophone GEMINI \/ OT871AG — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V 800mAh Li-ion cell is a direct replacement for the AT\u0026amp;T Gophone GEMINI and OT871AG. It fits the original battery compartment and connects to the same charge circuit used in both variants. No OEM part number is published for this cell, but the physical dimensions — 49.34 × 40.00 × 4.45mm — match the stock battery slot exactly.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eGEMINI and OT871AG compatibility:\u003c\/strong\u003e\n    Both devices share the same battery bay dimensions and 3.7V single-cell architecture. The charge management IC on each board accepts the same cutoff voltage, so one cell fits both without modification.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran a full charge-discharge cycle and confirmed the BMS held charge termination at 4.2V and triggered low-voltage cutoff cleanly. No thermal spikes during the CC-CV transition.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first use after installation, run one full discharge down to auto-shutoff, then charge uninterrupted to 100%. This gives the fuel gauge IC a complete reference curve for the new cell and prevents erratic percentage readings from the first day.\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 the Gophone GEMINI\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff issue, not a capacity problem. When the modem transmits or the screen runs at full brightness, current draw spikes and the cell voltage drops sharply below the BMS cutoff threshold — even if the fuel gauge still shows charge remaining. An aged or freshly installed uncalibrated cell hits this cliff earlier than expected. Run one full discharge-charge cycle and let the fuel gauge IC map the new cell's actual discharge curve. After calibration, the reported percentage and the real cutoff point align closer to 5–8% rather than 25–30%.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003ePhone won't power on after sitting in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells left uncharged below roughly 2.5V trigger a BMS lockout state — the battery stops responding to a standard charge handshake. The phone sees no valid cell voltage and won't boot. Connect the phone to a wall adapter, not a USB port on a computer, and leave it for 20–30 minutes without pressing the power button. The charge IC on the phone board sends a low-current recovery pulse that brings the cell back above the 2.5V re-enable threshold, after which normal charging resumes.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405100580954,"sku":"BWCS-OT880SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405100613722,"sku":"BWCS-OT880SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405100646490,"sku":"BWCS-OT880SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-OT880SL-1.webp?v=1779369970","url":"https:\/\/batteryweb.com\/products\/att-gophone-gemini-replacement-battery-37v-800mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}