{"product_id":"k-touch-u9-replacement-battery-38v-1550mah-li-ion","title":"K-Touch U9 AP18 Replacement Battery 3.8V 1550mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eK-Touch U9 — 3.8V Li-ion Replacement Battery (AP18)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.8V, 1550mAh Li-ion replacement cell for the K-Touch U9 smartphone. It fits the U9 model only and matches the OEM part number AP18. Install it when the original cell no longer holds a usable charge or fails to power the device.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eK-Touch U9 fitment:\u003c\/strong\u003e\n    The AP18 cell uses the same voltage rail, physical footprint (51.40 × 51.00 × 5.50mm), and connector pinout as the factory cell. The BMS communicates with the U9's charge IC on the same protocol — no adapter or modification needed.\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 a U9 unit and confirmed the BMS handshake, charge termination, and over-discharge cutoff all triggered at expected thresholds. The fuel gauge IC accepted the cell without error flags.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle fast charge tip:\u003c\/strong\u003e\n    On first use after installation, disable fast charging for one full discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.\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 K-Touch U9 after a cell swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe U9's fuel gauge IC stores a learned discharge curve from the original cell. When a new AP18 cell goes in, the IC still references the old curve. At around 20–30% reported charge, the new cell's actual voltage drops below what the modem and display draw can sustain — the phone shuts off even though the gauge reads capacity remaining. One complete slow discharge to 0% followed by a full uninterrupted charge resets the coulomb counter and aligns the gauge to the new cell. After that cycle, the shutdown threshold tracks correctly.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eOS battery percentage jumping erratically after replacement\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eErratic percentage jumps — such as dropping from 60% to 30% in seconds or bouncing between values — indicate the fuel gauge IC is recalibrating against an uncalibrated cell. This is not a fault with the cell itself. The IC's coulomb counter has no reference data for the AP18's actual capacity and internal resistance yet. Run two full discharge-charge cycles without interruption and without fast charging enabled; the percentage readout stabilises once the IC builds a consistent discharge profile. After the second cycle, charge the phone to 100% before normal use.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43404258017370,"sku":"BWCS-KTU900SL-1","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43404258050138,"sku":"BWCS-KTU900SL-2","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43404258082906,"sku":"BWCS-KTU900SL-3","price":28.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-KTU900SL-1.webp?v=1779369512","url":"https:\/\/batteryweb.com\/products\/k-touch-u9-replacement-battery-38v-1550mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}