{"product_id":"panasonic-kx-tca285-replacement-battery-37v-660mah-li-ion","title":"Panasonic KX-TCA285 Replacement Battery 3.7V 660mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003ePanasonic KX-TCA285 \/ KX-TCA385 Series — 3.7V Li-ion Replacement Battery (N4FUYYYY0047)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V 660mAh Li-ion battery replaces the factory cell in the Panasonic KX-TCA285, KX-TCA385, KX-UDT121, and KX-UDT131 wireless keyboards. It matches the OEM part numbers N4FUYYYY0047 and N4FUYYYY0046 and fits the same internal cell slot without modification. Dimensions are 40.00 × 31.10 × 5.90mm — measure your existing cell before ordering if you are unsure.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eKX-TCA \/ KX-UDT compatibility:\u003c\/strong\u003e\n    These four models share the same single-cell Li-ion bay, voltage rail, and connector spec. The KX-TCA285 and KX-TCA385 are Bluetooth wireless keyboards; the KX-UDT121 and KX-UDT131 are DECT cordless data-entry devices. All four draw from the same 3.7V cell with identical BMS handshake requirements.\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 the KX-TCA285 platform. The BMS accepted full charge without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold — no forced deep-discharge occurred during testing.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eRe-pairing after cell swap:\u003c\/strong\u003e\n    The KX-TCA285 and KX-TCA385 lose their Bluetooth pairing state when the cell drops below the BMS cutoff. After fitting a new battery, hold the pairing button on the underside of the keyboard for three seconds before attempting to reconnect to the host device.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the KX-TCA285 stops transmitting keystrokes before the battery indicator hits zero\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe KX-TCA285 uses a Bluetooth radio that draws a short current spike during each transmission burst. As the cell ages and internal resistance rises, that spike causes a momentary voltage sag below the radio's operating floor — even when the reported charge level still looks healthy. The keyboard cuts out mid-use because the radio browns out, not because the cell is truly empty. Replacing the cell restores the low internal resistance needed to sustain those transmission bursts cleanly.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eKeyboard still not recognised by the PC after fitting the new battery\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eA full power loss — including the brief gap during cell removal — clears the pairing memory on the KX-TCA285 and KX-TCA385. The host PC retains its side of the pairing, but the keyboard no longer responds to it. Delete the existing Bluetooth device entry on your PC, then hold the keyboard's pairing button until the LED blinks rapidly, and re-pair from scratch. Confirm the battery is reading above 3.6V before starting — a cell below that threshold may not power the Bluetooth radio long enough to complete the pairing handshake.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43377926242394,"sku":"BWCS-BMS770RC-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43377926275162,"sku":"BWCS-BMS770RC-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43377926307930,"sku":"BWCS-BMS770RC-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-BMS770RC-1.webp?v=1778366983","url":"https:\/\/batteryweb.com\/products\/panasonic-kx-tca285-replacement-battery-37v-660mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}