{"product_id":"deasy-t258-replacement-battery-37v-1200mah-li-ion","title":"DEASY T258 Compatible Battery 3.7V 1200mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eDEASY T258 \/ TL1266 \/ TS518 \/ TS808 — 3.7V Li-ion Replacement Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1200mAh (4.44Wh) Li-ion cell from DEASY's X-Longer series. It fits the T258 along with the TL1266, TS518, TS808, and six additional compatible models. It replaces cells that no longer hold a useful charge or have begun to swell.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eT258 \/ TL1266 \/ TS518 \/ TS808 platform fit:\u003c\/strong\u003e\n    These models share the same 3.7V single-cell architecture, connector pinout, and physical envelope (53.00 × 33.90 × 5.70mm), which is why one cell covers the full group. The BMS handshake and charge termination voltage are consistent across all listed variants.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through charge and discharge on compatible hardware, confirming BMS communication, correct charge termination at 4.2V, and stable output under combined screen and modem load. No false low-battery cutoff was triggered during testing.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installation, disable fast charging and run one complete discharge-to-charge cycle before resuming normal use. This allows the fuel gauge IC to map the new cell's discharge curve before high-current charging begins on an uncalibrated reference — skipping this step is the main cause of erratic percentage readings after a cell swap.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the T258 after a cell replacement\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff problem, not a capacity problem. When the modem transmits or the screen brightness peaks, current draw spikes sharply. A new cell with an uncalibrated fuel gauge IC can report 25% remaining while the actual open-circuit voltage is already near the low-cutoff threshold. The BMS reads a real undervoltage event and shuts down the phone to protect the cell — even though the percentage display says otherwise. One full discharge-charge cycle corrects the coulomb counter and pushes the shutdown threshold back to where it belongs, near 3.4–3.5V under load.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003ePhone won't power on after the replacement battery sat in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells self-discharge during storage. If the cell voltage has dropped below approximately 2.5V, the BMS enters a lockout state and will not pass current to the device — the phone shows no response to the power button. Connect the phone to a wall charger, not a PC port, and leave it for 15–20 minutes without pressing anything. The charge IC delivers a low-current trickle that slowly brings the cell voltage above the BMS re-enable threshold. Once the screen shows any charge indicator, normal charging can resume.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405031342170,"sku":"BWCS-NK5CHL-1","price":40.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405031374938,"sku":"BWCS-NK5CHL-2","price":47.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405031407706,"sku":"BWCS-NK5CHL-3","price":52.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-NK5CHL-1.webp?v=1779369842","url":"https:\/\/batteryweb.com\/products\/deasy-t258-replacement-battery-37v-1200mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}