{"product_id":"mustang-m31-replacement-battery-37v-900mah-li-ion","title":"Mustang M31 Replacement Battery 3.7V 900mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eMustang M31 — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 900mAh (3.33Wh) lithium-ion cell for the Mustang M31 smartphone. It replaces the original battery when the cell no longer holds a usable charge or fails to power the device. Dimensions are 46.20 × 34.14 × 5.68mm — confirm against your existing cell before fitting.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eM31 cell compatibility:\u003c\/strong\u003e\n    The M31 runs a compact battery bay sized for this specific footprint. A mis-sized cell will stress the connector tab and can lift the back cover. Match all three dimensions before installation.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled the cell through charge and discharge on the bench. The BMS accepted charge current correctly and voltage held steady through a full discharge without mid-cycle cutoff.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first use after installation, disable fast charging if available and run one full discharge-to-charge cycle. The fuel gauge IC on the M31 is calibrated to the original cell curve — a full cycle lets it map the new cell before resuming normal operation.\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 Mustang M31 after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens because the fuel gauge IC still references the old cell's discharge curve. When the new cell hits a voltage point the IC hasn't mapped yet, it can't accurately predict remaining capacity. Under load — screen-on, active data, or a call — voltage sags below what the IC expects, and the phone shuts down to protect the system. One full discharge and recharge cycle from 100% down to automatic shutdown, without interruption, lets the coulomb counter recalibrate against the new cell.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eM31 not powering on after the replacement cell sat in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells in storage self-discharge slowly. If the cell drops below approximately 2.5V, the BMS enters lockout mode and will not pass current to the device. The phone appears completely dead — no charge indicator, no boot. Connect the phone to a wall charger rather than a PC port and leave it for 15–20 minutes before attempting to power on; a wall adapter delivers enough current to push the BMS out of lockout where a low-amperage USB port may not.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405108183130,"sku":"BWCS-NK5BHL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405108215898,"sku":"BWCS-NK5BHL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405108248666,"sku":"BWCS-NK5BHL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-NK5BHL-1.webp?v=1779369992","url":"https:\/\/batteryweb.com\/products\/mustang-m31-replacement-battery-37v-900mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}