{"product_id":"umi-emax-replacement-battery-38v-3300mah-li-polymer","title":"UMI Emax Li3834t43p6h886740 Compatible Battery 3.8V 3300mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eUMI Emax \/ Hierro \/ Super — 3.8V Li-Polymer Replacement Battery (Li3834t43p6h886740)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.8V, 3300mAh lithium-polymer cell that replaces part number Li3834t43p6h886740 in the UMI Emax, Hierro, and Super smartphones. It matches the original cell's voltage, physical dimensions (87.34 × 65.42 × 3.80mm), and connector layout. Capacity is 3300mAh — 12.54Wh total energy.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eEmax, Hierro, and Super compatibility:\u003c\/strong\u003e\n    These three UMI models share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell covers all three — no hardware modification needed.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through charge, load, and cutoff on the Emax platform. The BMS accepted the cell without triggering a rejection flag, and charge termination fired correctly at 4.35V.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first cycle:\u003c\/strong\u003e\n    After fitting this cell, disable fast charging and run one full discharge-to-charge cycle at standard rate. The fuel gauge IC on these UMI models learns the new cell's discharge curve during that first cycle — skipping it leaves the coulomb counter calibrated to the old, degraded 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 UMI Emax reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe fuel gauge IC on the Emax stores a learned discharge curve from the original cell. When you install a fresh 3300mAh cell, that stored curve no longer matches actual cell behaviour. The gauge reads voltage and compares it against the old model, so it reports percentage values that are off — sometimes by 15–20%. One full standard-rate discharge-charge cycle rewrites the reference curve and brings the display back into alignment.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% remaining on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff event — not a capacity fault. Under heavy load (modem handoff, screen at full brightness, or background sync), the cell's terminal voltage drops faster than the fuel gauge expects from the old discharge model. The system hits the hardware undervoltage threshold before the percentage counter reaches zero and shuts down immediately. Let the phone sit powered off for two minutes after shutdown, then charge to 100% without interruption. After two full cycles, the gauge model updates and the cliff shifts back below 10%.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404161384538,"sku":"BWCS-TCP728SL-1","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404161417306,"sku":"BWCS-TCP728SL-2","price":28.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404161450074,"sku":"BWCS-TCP728SL-3","price":31.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-TCP728SL-1.webp?v=1779369270","url":"https:\/\/batteryweb.com\/products\/umi-emax-replacement-battery-38v-3300mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}