{"product_id":"ntt-docomo-f-04b-replacement-battery-37v-600mah-li-ion","title":"NTT DoCoMo F-04B Smartphone Li-ion Compatible Battery 3.7V 600mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eNTT DoCoMo F-04B — 3.7V Li-ion Replacement Battery (F13 \/ AAF29134)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V, 600mAh Li-ion cell replaces the original battery in the NTT DoCoMo F-04B smartphone. It matches the OEM voltage rail and physical footprint, fitting directly into the F-04B battery bay. Capacity is sourced from manufacturer spec — 600mAh, 2.22Wh.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eF-04B cell fit:\u003c\/strong\u003e\n    The F-04B uses a compact 44.15 × 39.22 × 3.70mm cell with a 3.7V nominal rail. This replacement matches those dimensions and voltage exactly, so the connector seats without modification and the BMS handshake completes normally 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 charge and discharge on the bench. The BMS accepted charge current without tripping, held voltage above the low-battery cutoff threshold at end of discharge, and reported cell status cleanly to the host device throughout.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installing a new cell, run one full discharge to automatic shutdown, then charge uninterrupted to 100% before resuming normal use. The F-04B's fuel gauge IC calibrates its coulomb counter against this first full cycle — skipping it causes the percentage display to read inaccurately for days.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the F-04B reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe F-04B tracks battery state using a fuel gauge IC that builds a discharge curve over time. When you replace the cell, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The IC keeps applying the old curve, so the percentage it reports drifts from reality — sometimes by 15–20%. One complete discharge-to-shutdown followed by a full uninterrupted charge 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% remaining on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the cell voltage drops sharply under load before the fuel gauge expects it — a voltage cliff. On a fresh cell that hasn't been calibrated, the gauge overestimates remaining charge. When the modem or display draws a spike of current, cell voltage sags below the BMS cutoff threshold and the phone shuts off instantly. The fix is the same calibration cycle: full discharge to shutdown, then charge to 100% without interruption. After one complete cycle the gauge tracks the actual voltage curve and the early shutdowns stop.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405096386650,"sku":"BWCS-NDF13SL-1","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405096419418,"sku":"BWCS-NDF13SL-2","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405096452186,"sku":"BWCS-NDF13SL-3","price":28.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-NDF13SL-1.webp?v=1779369970","url":"https:\/\/batteryweb.com\/products\/ntt-docomo-f-04b-replacement-battery-37v-600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}