{"product_id":"consumer-cellular-envoy-u3900-replacement-battery-37v-950mah-li-ion","title":"Consumer Cellular Envoy U3900 Replacement Battery 3.7V 950mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eConsumer Cellular Envoy U3900 — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V 950mAh (3.52Wh) Li-ion replacement battery for the Consumer Cellular Envoy U3900. The Envoy U3900 is a simplified mobile phone built for seniors and users who want straightforward calls and texts. Swap this in when the original cell can no longer hold a charge or fails to power the device.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eEnvoy U3900 fit:\u003c\/strong\u003e\n    This battery matches the U3900's physical footprint at 53.78 × 34.05 × 4.80mm and connects to the phone's charge IC at 3.7V nominal — the voltage the modem and baseband processor expect under load.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through full discharge and charge sequences on the bench. The BMS held stable cutoff at both ends, and the charge IC accepted the cell without triggering fault flags.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration after swap:\u003c\/strong\u003e\n    On first use after installation, run one complete discharge down to automatic shutdown, then charge to 100% without interruption. This lets the phone's fuel gauge IC map the new cell's actual discharge curve before it starts reporting percentage to the OS.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Envoy U3900 reports the wrong battery percentage after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe U3900 tracks charge state using a fuel gauge IC that builds a model of the cell's discharge curve over time. When you install a new cell, that model still reflects the old battery's characteristics — not the new one. The IC reads voltage and maps it to a percentage using stale reference data, so the number on screen can be off by 10–20%. One full discharge-charge cycle gives the IC enough data to rebuild its model against the new cell and report accurately.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% remaining on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the fuel gauge IC hasn't finished calibrating to the new cell's voltage curve. Under load — a call connecting, the screen at full brightness — the cell voltage drops sharply at a point the IC still maps to 20–30%. The phone's protection circuit reads that as a valid shutdown threshold and cuts power. Run one complete discharge cycle to let the coulomb counter anchor to the new cell's actual low-voltage cliff, which typically sits near 3.0–3.2V under the U3900's load profile.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404313329754,"sku":"BWCS-HUM318XL-1","price":28.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404313362522,"sku":"BWCS-HUM318XL-2","price":32.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404313395290,"sku":"BWCS-HUM318XL-3","price":34.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-HUM318XL-1.webp?v=1779369680","url":"https:\/\/batteryweb.com\/products\/consumer-cellular-envoy-u3900-replacement-battery-37v-950mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}