{"product_id":"i-mate-ultimate-8502-replacement-battery-37v-1600mah-li-polymer","title":"I-Mate Ultimate 8502 Replacement Battery 303POL0000A 3.7V","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eI-Mate Ultimate 8502 — 3.7V Li-Polymer Replacement Battery (303POL0000A)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V, 1600mAh Li-Polymer cell is a direct swap for the battery in the I-Mate Ultimate 8502 Windows Mobile smartphone. It matches the original part number 303POL0000A and the alternate reference 745WS00685. At 5.92Wh and 66.89 x 44.37 x 4.71mm, it fits the original battery bay without modification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eUltimate 8502 fitment:\u003c\/strong\u003e\n    The 8502 uses a dedicated Li-Polymer cell with a fixed connector pinout tied to the device's charge IC and fuel gauge circuit. This cell matches that pinout, voltage rail, and physical footprint — so the BMS handshake completes correctly on first boot.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through a full charge and discharge sequence, monitoring BMS cutoff behaviour at both the high-voltage ceiling and the low-voltage floor. The protection circuit tripped correctly at each threshold with no false cutoffs under steady load.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installation, run one complete discharge-charge cycle with fast charging disabled. This gives the fuel gauge IC a clean reference curve against the new cell before high-current charging begins on an uncalibrated counter.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Ultimate 8502 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe 8502 uses a fuel gauge IC that tracks charge state by measuring cumulative current flow — a coulomb-counting method. When you swap the cell, the IC still holds the discharge curve it built around the old, degraded cell. The new cell has a different impedance profile, so the gauge drifts from the actual state of charge immediately. One full discharge-to-cutoff and charge-to-100% cycle resets the reference and brings the percentage readout back in line with real capacity.\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 has not yet recalibrated to the new cell's discharge curve. At around 3.6–3.5V, the modem radio or screen backlight draws a current spike the gauge wasn't predicting at that state of charge, and the BMS cuts power to protect the cell. It looks like a random crash but it is a voltage cliff the old curve did not map correctly. Complete two full discharge-charge cycles without fast charging — after that, the coulomb counter tracks the new curve accurately and the shutdowns stop.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405203406938,"sku":"BWCS-MU8502SL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405203439706,"sku":"BWCS-MU8502SL-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405203472474,"sku":"BWCS-MU8502SL-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-MU8502SL-1.webp?v=1779370333","url":"https:\/\/batteryweb.com\/products\/i-mate-ultimate-8502-replacement-battery-37v-1600mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}