{"product_id":"telefunken-eurofon-t20-replacement-battery-37v-600mah-li-ion","title":"Telefunken Eurofon T20 Compatible Battery 3.7V 600mAh PHBA-309","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eTelefunken Eurofon T20 — 3.7V Li-ion Replacement Battery (PHBA-309)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V 600mAh Li-ion replacement battery for the Telefunken Eurofon T20 mobile phone. It replaces OEM part number PHBA-309 when the original cell has degraded or failed. The Eurofon T20 is a compact early-2000s handset with a small battery bay sized to this cell's 41.54 x 41.54 x 4.47mm footprint.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eEurofon T20 fit:\u003c\/strong\u003e\n    The T20 uses a single Li-ion cell on a 3.7V nominal rail. This replacement matches the original connector pinout and physical dimensions, so the battery bay closes flush 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 full charge and discharge on the T20 platform and confirmed the BMS holds charge termination correctly at 4.2V without triggering an overcharge fault on the host device's charge IC.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first install:\u003c\/strong\u003e\n    On first use, run one complete discharge down to automatic cutoff, then charge uninterrupted to 100%. This lets the T20's fuel gauge IC map the new cell's discharge curve before reporting percentage to the display.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Eurofon T20 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe T20's fuel gauge IC stores a learned discharge curve from the original cell. A new cell has a different internal resistance profile, so the stored curve no longer matches actual charge state. The gauge reads voltage and maps it against old data, producing percentage values that are off by 10–25%. One full discharge-charge cycle forces the IC to re-anchor its coulomb counter against the new cell's actual endpoint voltage of approximately 3.0V cutoff.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the Eurofon T20\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the cell voltage drops sharply under load — a voltage cliff — before the displayed percentage reaches zero. On a 600mAh cell, even brief high-current draws from the radio transmitter or backlight can pull cell voltage below the BMS protection threshold of around 3.0V while the gauge still reads 20–30%. It is not a faulty battery; it means the fuel gauge IC has not yet calibrated to the new cell. Complete one full uninterrupted discharge cycle and the shutdowns will stop once the gauge correctly identifies the cell's true low-voltage floor.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405076430938,"sku":"BWCS-HFE200SL-1","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405076463706,"sku":"BWCS-HFE200SL-2","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405076496474,"sku":"BWCS-HFE200SL-3","price":28.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-HFE200SL-1.webp?v=1779369919","url":"https:\/\/batteryweb.com\/products\/telefunken-eurofon-t20-replacement-battery-37v-600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}