{"product_id":"microsoft-lumia-640-replacement-battery-38v-2600mah-li-ion","title":"BV-T5C Microsoft Lumia 640 Compatible Battery 3.8V 2600mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eMicrosoft Lumia 640 — 3.8V Li-ion Replacement Battery (BV-T5C)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.8V, 2600mAh Li-ion replacement battery for the Microsoft Lumia 640 smartphone (RM-1072, RM-1073). It replaces the original BV-T5C cell when the existing battery degrades, fails to hold charge, or triggers unexpected shutdowns. Capacity figures come from the product data: 2600mAh \/ 9.88Wh.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eLumia 640 compatibility (RM-1072 \/ RM-1073):\u003c\/strong\u003e\n    Both RM-1072 and RM-1073 variants share the same BV-T5C footprint, connector pinout, and BMS handshake protocol. The charge IC on these boards negotiates at 3.8V nominal — this cell matches that rail exactly.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell in an RM-1073 unit under screen-on and modem-active load. The BMS accepted charge without fault flags, and voltage held stable through full discharge without premature cutoff.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fuel gauge recalibration:\u003c\/strong\u003e\n    After fitting this cell, disable fast charging and run one complete discharge-charge cycle at standard rate. The Lumia 640's fuel gauge IC is calibrated to the old cell's discharge curve — one full cycle at low current lets it re-anchor against the new cell 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 Lumia 640 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Lumia 640 uses a coulomb counter inside the fuel gauge IC to track charge state. That counter builds its reference model against the original cell's specific discharge curve over many cycles. When a new cell goes in, the stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The gauge reads accurately at 100% and 0% but drifts badly in between — most noticeably between 20% and 60%. One full discharge down to automatic shutdown followed by a full charge corrects this without any manual steps.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff issue, not a capacity problem. Under peak load — LTE modem transmitting, screen at full brightness — the cell voltage sags momentarily below the BMS cutoff threshold even though the gauge still shows charge remaining. The original BV-T5C cell in a worn phone behaves the same way late in its life, so the OS shutdown threshold was never tuned for this edge. Run the phone through two full discharge-charge cycles at standard charge rate; the fuel gauge IC recalibrates its low-voltage prediction and the premature shutdowns stop. If they continue after two cycles, check that battery connector contacts on the board are fully seated and free of corrosion.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404134907994,"sku":"BWCS-NK641XL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404134940762,"sku":"BWCS-NK641XL-2","price":29.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404134973530,"sku":"BWCS-NK641XL-3","price":32.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-NK641XL-1.webp?v=1779369060","url":"https:\/\/batteryweb.com\/products\/microsoft-lumia-640-replacement-battery-38v-2600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}