{"product_id":"cisco-cp-8821-ex-k9-bun-replacement-battery-38v-2400mah-li-polymer","title":"Cisco CP-8821 Cordless Phone Replacement Battery 3.8V 2400mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eCisco Wireless IP Phone 8821 — 3.8V Li-Polymer Replacement Battery (CP-BATT-8821)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.8V, 2400mAh (9.12Wh) lithium-polymer battery for the Cisco CP-8821 series wireless IP phone. It fits the CP-8821, CP-8821-K9-BUN, and CP-8821-EX-K9-BUN handsets. Swap it in when the original pack no longer holds a charge through a full shift.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eCP-8821 series compatibility:\u003c\/strong\u003e\n    The CP-8821, CP-8821-K9-BUN, and CP-8821-EX-K9-BUN all share the same 3.8V battery bay, connector pinout, and BMS handshake protocol — one pack covers the entire lineup.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this pack through charge cycles on a CP-8821 handset. The BMS accepted charge from the base station cradle without a fault flag, and cell voltage held stable across the full charge curve.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle conditioning on the CP-8821:\u003c\/strong\u003e\n    After fitting this battery, seat the handset in the base cradle and leave it for a full charge cycle before making calls. Li-polymer cells shipped at storage charge need one complete charge to calibrate the handset's fuel gauge — skipping this causes the battery indicator to read inaccurately for weeks.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the CP-8821 shows a shorter charge bar right after battery replacement\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe CP-8821 tracks battery state using a coulomb counter that learns from full charge-discharge cycles. A new cell arrives at roughly 40–50% storage charge, so the counter starts with no calibration reference. The handset reads this as a partial or degraded pack, not a fresh one. Run two full charge cycles — charge to 100% in the cradle, use the phone until it prompts a low-battery warning — and the gauge corrects itself.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBase cradle charge light not activating after battery swap\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the replacement cell's resting voltage sits below the base station's charge-acceptance threshold — common after extended storage. The base reads the low voltage as a fault condition rather than a dischargeable pack and refuses to initiate charge. Remove the handset from the cradle, leave it out for 30 seconds, then re-seat it firmly so the charging contacts close cleanly. If the charge light still does not activate, use a USB-C cable to trickle charge the handset directly to 3.6V before returning it to the cradle.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43339881349210,"sku":"BWCS-CIP823CL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43339881381978,"sku":"BWCS-CIP823CL-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43339881414746,"sku":"BWCS-CIP823CL-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-CIP823CL-1.webp?v=1778366843","url":"https:\/\/batteryweb.com\/products\/cisco-cp-8821-ex-k9-bun-replacement-battery-38v-2400mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}