{"product_id":"xiaomi-max-2-replacement-battery-385v-5300mah-li-polymer","title":"Xiaomi Mi Max 2 BM50 Replacement Battery 3.85V 5300mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eXiaomi Mi Max 2 — 3.85V Li-Polymer Replacement Battery (BM50)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.85V, 5300mAh (20.41Wh) Li-Polymer replacement cell for the Xiaomi Mi Max 2 smartphone. It fits the MDE40 and MDT40 variants alongside the standard Max 2. When the original BM50 cell degrades, capacity drops sharply on a phone this large — swapping the cell brings the device back to full charge capacity.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eMax 2 \/ MDE40 \/ MDT40 fit:\u003c\/strong\u003e\n    All three variants share the same battery bay geometry, connector pinout, and BMS handshake protocol. The BM50 footprint — 104.10 × 76.40 × 3.40mm — is consistent across this entire model group, so no adapter or modification is needed.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell through charge and discharge cycles on the Mi Max 2 platform. The BMS accepted charge without tripping over-current protection, and the fuel gauge IC tracked state-of-charge accurately after a full calibration cycle.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fuel gauge reset:\u003c\/strong\u003e\n    On first use after installation, disable fast charging and run one complete discharge down to automatic shutdown, then charge fully on a standard 5V\/2A input. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging begins.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Mi Max 2 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Mi Max 2 uses a coulomb-counting fuel gauge IC that builds its state-of-charge model against the original cell's discharge curve over hundreds of cycles. When a new cell goes in, that learned curve no longer matches the cell's actual chemistry. The gauge reads a stale model, so it may show 40% and then cut off — or show 15% while the phone keeps running. One complete discharge-to-shutdown followed by a full charge resets the coulomb counter to the new cell's real endpoints. After that cycle, percentage readings stabilise.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens because the modem and the large 6.44-inch display on the Mi Max 2 pull current spikes that cause a voltage sag on a freshly installed cell. If the cell voltage dips below the BMS cutoff threshold under that combined load — even briefly — the BMS trips and shuts the phone down before the gauge reads zero. It is not a faulty cell; it is the fuel gauge misreading available capacity before calibration. Run the first-cycle calibration discharge at lower screen brightness and with mobile data active so the load mirrors real-world use. After calibration, the BMS cutoff and the gauge reading align, and the shutdowns stop.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43392072548442,"sku":"BWCS-MUE400XL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43392072581210,"sku":"BWCS-MUE400XL-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43392072613978,"sku":"BWCS-MUE400XL-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-MUE400XL-1.webp?v=1779143621","url":"https:\/\/batteryweb.com\/products\/xiaomi-max-2-replacement-battery-385v-5300mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}