{"product_id":"tetra-cassidian-thr9-replacement-battery-37v-5200mah-li-ion","title":"TETRA Cassidian THR9 Replacement Battery BLN-5i 3.7V 5200mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eTETRA Cassidian THR9 — 3.7V Li-ion Replacement Battery (BLN-5i)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V, 5200mAh Li-ion battery replaces the OEM BLN-5i, BLN-6, and BLN-Ex-2 U packs used in the Cassidian THR9 TETRA portable radio. It also fits the HT9588AA and HR8509AA variants. All specs match the original: same voltage rail, same cell chemistry, same connector and BMS handshake profile.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eTHR9 platform compatibility:\u003c\/strong\u003e\n    The THR9, HT9588AA, and HR8509AA share the same battery bay, locking tab geometry, and BMS communication protocol — one pack covers all three. Swapping between variants needs no adapters or firmware changes.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this pack through repeated PTT transmit bursts on the THR9 platform. The BMS held stable under the transmit current spike and did not trigger an overcurrent cutoff during sustained RF output.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eContact strip initialisation on first dock insertion:\u003c\/strong\u003e\n    If the charger shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The THR9 charger requires a clean contact cycle to complete the BMS handshake before charging begins.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the THR9 drops to reduced TX power mid-shift on a fresh pack\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe THR9 monitors battery voltage in real time and steps down transmit power when voltage sags below its RF output threshold. A new cell shipped at storage voltage — typically around 3.6V — can trigger this behaviour under sustained high-power transmission before the first full charge cycle. The radio is not faulty and the pack is not defective. Run one full charge cycle before the first operational shift and the voltage sag under load will stay within the radio's acceptable TX power window.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBar indicator showing one fewer bar than expected after inserting a new BLN-5i\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe THR9 uses a voltage-threshold bar indicator — each bar corresponds to a fixed voltage band. New cells leave the warehouse at partial storage charge, not full charge, so the indicator correctly reads one or two bars low on first insertion. This is not a capacity defect. Seat the pack in the OEM charger and run a complete charge cycle until the dock shows full. After that first cycle the indicator will read the full charge state accurately.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43426298134618,"sku":"BWCS-ETH910TW-1","price":42.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43426298167386,"sku":"BWCS-ETH910TW-2","price":49.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43426298200154,"sku":"BWCS-ETH910TW-3","price":54.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-ETH910TW-1.webp?v=1779930583","url":"https:\/\/batteryweb.com\/products\/tetra-cassidian-thr9-replacement-battery-37v-5200mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}