{"product_id":"doro-primo-366-replacement-battery-37v-1200mah-li-ion","title":"Doro Primo 366 Replacement Battery RCB01P04 3.7V 1200mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eDoro Primo 366 — 3.7V Li-ion Replacement Battery (RCB01P04)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1200mAh Li-ion cell built to replace the original battery in the Doro Primo 366. The Primo 366 is a simplified mobile phone aimed at users who need clear calling and straightforward texting — nothing more. When the original cell degrades and the phone cuts out unexpectedly or refuses to hold charge, this replacement restores the device to full working condition.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003ePrimo 366 fitment:\u003c\/strong\u003e\n    The Primo 366 uses a removable flat-cell format at 62.18 × 38.14 × 4.50mm. This cell matches that footprint precisely, including the connector position required for the phone's charge IC to communicate with the battery correctly.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran charge cycles on this cell and confirmed the BMS accepted standard charging current without triggering a protection cutoff. Capacity held steady across multiple cycles, and the cell did not trip the low-voltage lockout under simulated call and screen load.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration after install:\u003c\/strong\u003e\n    On first use, run the phone from a full charge down to automatic shutdown — do not charge before shutdown. This gives the fuel gauge IC one complete reference cycle against the new cell's discharge curve before the OS starts reporting percentage.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Primo 366 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Primo 366 uses a fuel gauge IC that builds its charge estimate against a stored discharge curve from the previous cell. Swap in a new cell and that stored curve no longer matches — the IC will report percentages that drift from actual state of charge. This shows up most often as the phone jumping from 40% to 15% with no load change, or reporting 100% when the cell is clearly not full. One full discharge-charge cycle resets the coulomb counter and re-anchors the IC to the new cell's actual curve.\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 happens when the cell voltage drops sharply under the current draw of an active call or backlit screen — a voltage cliff the fuel gauge IC did not anticipate. The phone's protection circuit reads voltage collapse as a low-battery emergency and shuts down immediately, even though the displayed percentage appeared safe. The root cause is an uncalibrated fuel gauge, not a faulty cell. Complete one full discharge cycle to let the IC map the new cell's voltage curve, and shutdowns at false percentages will stop.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404130615386,"sku":"BWCS-BES140SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404130648154,"sku":"BWCS-BES140SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404130680922,"sku":"BWCS-BES140SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-BES140SL-1.webp?v=1779369036","url":"https:\/\/batteryweb.com\/products\/doro-primo-366-replacement-battery-37v-1200mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}