{"product_id":"maxcom-mm720-replacement-battery-37v-800mah-li-ion","title":"MaxCom MM720 Replacement Battery 3.7V 800mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eMaxCom MM720 \/ MM721 Series — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V, 800mAh Li-ion cell replaces the original battery in the MaxCom MM720, MM720BB, MM721, and MM721BB mobile phones. These are compact, basic handsets aimed at elderly users and emergency-use scenarios where keeping the phone powered matters. The replacement cell matches the original voltage and physical footprint at 66.60 × 33.90 × 4.50mm.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eMM720 and MM721 platform fit:\u003c\/strong\u003e\n    Both model lines share the same battery bay dimensions, connector pitch, and 3.7V nominal voltage rail. The BB variants use the same housing, so a single cell covers all four listed models without modification.\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 MM720 unit. The BMS accepted the charge handshake without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold, as expected on a single-cell Li-ion pack.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installing this cell, run one full discharge to auto-off, then charge uninterrupted to 100% before normal use. The MM720's fuel gauge IC is calibrated to the old cell's discharge curve — skipping this step causes the percentage counter to read inaccurately for weeks.\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 MM720 after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens because the fuel gauge IC still references the discharge curve of the original, degraded cell. When a fresh cell with a steeper voltage drop hits load from the radio or screen backlight, the IC interprets the voltage dip as a near-empty state and triggers shutdown. The phone cuts out even though usable charge remains. One full discharge-charge cycle resets the coulomb counter and brings the percentage readout in line with actual cell state — after that, early shutdowns stop.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003ePhone won't power on after sitting in storage with the new battery installed\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells self-discharge during storage. If the MM720 sat unused long enough for the cell to drop below approximately 2.5V, the BMS enters lockout mode to prevent cell damage — and the phone shows no response to the power button. Connect the phone to a wall charger, not a USB port, and leave it for 20–30 minutes without pressing anything. Most BMS circuits on cells like this will accept a trickle current above the lockout threshold and begin recovery; the charge indicator should appear within that window.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404179963994,"sku":"BWCS-KMB400SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404179996762,"sku":"BWCS-KMB400SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404180029530,"sku":"BWCS-KMB400SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-KMB400SL-1.webp?v=1779369289","url":"https:\/\/batteryweb.com\/products\/maxcom-mm720-replacement-battery-37v-800mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}