{"product_id":"kenwood-nx-p500-replacement-battery-37v-1800mah-li-ion","title":"Kenwood KNB-81L Two-Way Radio Replacement Battery 3.7V 1800mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eKenwood NX-P500 \/ PKT-300 \/ TK-3601D — 3.7V Li-ion Replacement Battery (KNB-81L)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1800mAh Li-ion replacement battery for the Kenwood NX-P500, PKT-300, and TK-3601D portable two-way radios. It replaces OEM part numbers KNB-81L and KNB-81LI. The pack fits the original battery bay directly and uses the same connector and BMS communication protocol as the factory unit.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eNX-P500, PKT-300, TK-3601D fit group:\u003c\/strong\u003e\n    These three radios share the same 3.7V battery bay, connector pinout, and BMS handshake protocol. One pack covers all three without modification or adapter.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this pack on the NX-P500 through repeated PTT transmit bursts and monitored BMS response. The overcurrent protection tripped correctly on fault simulation and reset cleanly on power cycle. Voltage held within spec across the full discharge curve.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst insertion into the charger dock:\u003c\/strong\u003e\n    If the dock LED shows a fault or blinks amber on first insertion, remove the pack and wipe the gold contact strip with a dry cloth. Reseat it firmly. The Kenwood dock requires a clean contact cycle to complete the BMS handshake before it will begin charging.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the NX-P500 drops to reduced TX power mid-shift on a new battery\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe NX-P500 monitors pack voltage in real time and steps down transmit power when voltage sags below its internal threshold. A new cell shipped at storage voltage — typically around 3.6V — has less headroom than a fully charged pack at 4.2V. Under sustained RF output, that sag crosses the radio's protection floor faster than expected. Charge the pack to full before the first shift and the TX power will hold at rated output throughout normal use.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBar indicator showing one fewer bar than expected after inserting a new KNB-81L\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe NX-P500 uses voltage-threshold bar indicators, not a fuel gauge chip. A new pack leaves the warehouse at storage voltage, roughly 3.6–3.7V, which the radio correctly reads as a partially charged cell. This is not a fault — the cell has full capacity but is not at full charge voltage. Place the pack in the dock, allow a complete charge cycle until the LED goes green, and the indicator will show full bars at 4.2V.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43426285584474,"sku":"BWCS-KNB810TW-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43426285617242,"sku":"BWCS-KNB810TW-2","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43426285650010,"sku":"BWCS-KNB810TW-3","price":33.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-KNB810TW-1.webp?v=1779930600","url":"https:\/\/batteryweb.com\/products\/kenwood-nx-p500-replacement-battery-37v-1800mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}