{"product_id":"auro-m401-replacement-battery-37v-1000mah-li-ion","title":"Auro M401 Replacement Battery 3.7V 1000mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAuro M401 — 3.7V Li-ion Replacement Battery (M451)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1000mAh Li-ion replacement battery for the Auro M401 smartphone. It fits the M401 directly and uses OEM part number M451. When the original cell degrades after repeated charge cycles, this battery restores the phone to full operation.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eM401 platform fit:\u003c\/strong\u003e\n    The M401 uses a single-cell 3.7V nominal rail with a connector and physical footprint matched to the M451 part number. The BMS handshake on this device authenticates the cell by voltage and thermistor signal — both are met by this replacement cell.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran the cell through charge and discharge cycles on the M401 platform. The BMS accepted the cell on first insertion, charge termination triggered correctly at full voltage, and the protection circuit tripped as expected under short-circuit simulation.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first installation, disable fast charging if available and run one full discharge-to-charge cycle before normal use. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging begins on an uncalibrated state-of-charge reading.\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 Auro M401 after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens because the fuel gauge IC on the M401 is still using the discharge curve from the old, degraded cell. The new cell has a steeper voltage cliff under load — particularly when the modem or display draws current — so the phone hits the undervoltage cutoff while the percentage reading is still showing 20–30%. It is not a fault in the replacement cell. One full discharge-charge cycle recalibrates the coulomb counter and the shutdowns stop.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003ePhone reports incorrect battery percentage after replacement\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe M401's fuel gauge IC stores a learned discharge model for the previous cell. After swapping to a new cell, that stored model is mismatched — the percentage shown is calculated against the wrong capacity baseline. The fix is a full calibration cycle: drain the phone to automatic shutdown, then charge uninterrupted to 100% without removing the cable. After one complete cycle the IC resets its reference points and percentage readings stabilise.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405083312218,"sku":"BWCS-ARM401SL-1","price":21.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405083344986,"sku":"BWCS-ARM401SL-2","price":24.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405083377754,"sku":"BWCS-ARM401SL-3","price":26.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-ARM401SL-1.webp?v=1779369918","url":"https:\/\/batteryweb.com\/products\/auro-m401-replacement-battery-37v-1000mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}