{"product_id":"asus-transformer-aio-p1801-tablet-pc-replacement-battery-74v-5000mah-li-polymer","title":"Asus C21-P1801 Replacement Battery 7.4V 5000mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAsus Transformer AiO P1801 Tablet PC — 7.4V Li-Polymer Replacement Battery (C21-P1801)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 7.4V, 5000mAh (37Wh) Li-Polymer cell replaces the original C21-P1801 battery in the Asus Transformer AiO P1801 hybrid tablet-desktop. It fits the detachable touchscreen tablet unit, not the docking base. Confirmed compatible with P1801, AP180C, P18Y23, and P1801-B040K variants.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eP1801 tablet unit compatibility:\u003c\/strong\u003e\n    The AiO P1801 splits into a Windows 8 all-in-one desktop and a detachable Android tablet. This battery powers only the tablet portion. All listed variants — P1801, AP180C, P18Y23, P1801-B040K — share the same tablet unit, the same C21-P1801 connector pinout, and the same BMS handshake voltage thresholds.\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 P1801 tablet unit. The BMS accepted the cell without error flags, charge current ramped correctly through CC\/CV phases, and the protection circuit triggered cleanly at low-voltage cutoff.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003ePost-install calibration on the P1801:\u003c\/strong\u003e\n    After fitting this cell, run one full discharge to hibernate-cutoff, then charge uninterrupted to 100%. The P1801's fuel gauge IC calibrates against the new cell's actual capacity — skipping this step leaves the percentage readout unreliable for the first several use cycles.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the P1801 tablet shows \"poor battery health\" immediately after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe P1801 stores historical charge data in EEPROM on the battery's protection circuit board. When a new cell goes in, the system reads that EEPROM as blank or mismatched and flags poor health — even though the cell is brand new. This is a data state, not a hardware fault. Running a full discharge-to-cutoff followed by an uninterrupted charge to 100% resets the battery learn cycle and clears the warning. After two or three complete cycles, the OS health indicator updates to reflect the actual cell condition.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eP1801 tablet shutting down at 20–30% shown on the gauge\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the cell voltage drops below the BMS cutoff threshold before the fuel gauge reaches zero. The gauge IC calculated remaining capacity based on old cycle data — it expected the cell to hold voltage longer than it actually did. The fix is a full calibration cycle: discharge to automatic hibernate, do not force-shutdown, then charge to 100% without interruption. After two full cycles the gauge IC re-maps the voltage curve against the new cell, and the shutdown-at-30% behaviour stops.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43409651826778,"sku":"BWCS-AUT180NB-1","price":47.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43409651859546,"sku":"BWCS-AUT180NB-2","price":54.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43409651892314,"sku":"BWCS-AUT180NB-3","price":60.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-AUT180NB-1.webp?v=1779580296","url":"https:\/\/batteryweb.com\/products\/asus-transformer-aio-p1801-tablet-pc-replacement-battery-74v-5000mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}