{"product_id":"mcgrey-mc-50b-replacement-battery-37v-1200mah-li-ion","title":"McGrey MC-50B Replacement Battery 3.7V 1200mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eMcGrey MC-50B — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1200mAh Li-ion battery for the McGrey MC-50B smartphone. It fits the MC-50B directly and restores power when the original cell has degraded past usable capacity. Dimensions are 53.00 × 33.90 × 5.70mm — confirm these against your existing cell before fitting.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eMC-50B cell compatibility:\u003c\/strong\u003e\n    The MC-50B runs a single-cell 3.7V nominal architecture. This replacement matches that voltage rail and physical footprint, so the charge IC sees the correct cell parameters at startup.\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 a smartphone test rig, confirming BMS handshake, charge acceptance from 0%, and stable voltage at the protection cutoff threshold.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration after swap:\u003c\/strong\u003e\n    On first use after installation, disable fast charging for one full discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.\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 MC-50B after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eA new cell has a slightly different internal resistance profile than the aged cell the fuel gauge IC was calibrated to. Under screen or modem load, the cell voltage drops faster than the gauge predicts, hitting the hardware cutoff before the displayed percentage reaches zero. The phone sees a hard voltage floor — not a software decision — and shuts down immediately. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and pushes the shutdown threshold back down to the correct level.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eMC-50B not powering on after the replacement cell sat in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells self-discharge during storage, and if voltage drops below roughly 2.5V the BMS trips into lockout to prevent damage to the cell. The phone will show no response on the power button — not even a charge indicator. Connect to a wall charger, not a USB port, and leave it for 15–20 minutes before attempting to power on. Once the BMS sees voltage climb above its recovery threshold, typically around 2.9–3.0V, it releases the lockout and normal charging resumes.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404286361690,"sku":"BWCS-DEP215SL-1","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404286394458,"sku":"BWCS-DEP215SL-2","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404286427226,"sku":"BWCS-DEP215SL-3","price":28.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-DEP215SL-1.webp?v=1779369550","url":"https:\/\/batteryweb.com\/products\/mcgrey-mc-50b-replacement-battery-37v-1200mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}