{"product_id":"tetra-cassidian-thr9-replacement-battery-37v-2300mah-li-ion","title":"TETRA Cassidian THR9 BLN-5i Replacement Battery 3.7V 2300mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eTETRA Cassidian THR9 \/ HT9588AA — 3.7V Li-ion Replacement Battery (BLN-5i)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 2300mAh Li-ion replacement battery for the Cassidian THR9 TETRA portable radio and compatible variants including the HT9588AA and HR8509AA. It replaces OEM part numbers BLN-5i, BLN-6, and BLN-Ex-2 U. The THR9 is a professional digital radio used in public safety, security, and commercial communications environments.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eTHR9 \/ HT9588AA \/ HR8509AA platform fit:\u003c\/strong\u003e\n    These three models share the same battery bay geometry, contact layout, and BMS handshake protocol. A single cell pack with the correct 3.7V rail and BLN-5i form factor fits all three without modification.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this pack through full charge and discharge passes on the THR9 platform. The BMS accepted charge current without fault, held voltage through simulated PTT transmit load spikes, and released to the charger dock cleanly on each cycle.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst insertion into charger dock:\u003c\/strong\u003e\n    If the dock shows a fault LED on first insertion, remove the pack, wipe the gold contact strip with a dry cloth, and reseat firmly. The THR9 dock requires a clean contact cycle to register the new BMS 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 cuts out mid-transmission on a new BLN-5i pack\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe THR9 draws a sharp current spike the moment PTT is pressed — RF output, speaker drive, and digital baseband all load the cell simultaneously. A new pack shipped at storage voltage (typically around 3.6V) sits close to the BMS undervoltage threshold before any real discharge has occurred. That spike can momentarily pull the cell below the cutoff, triggering a BMS trip and killing the transmission. Run one full charge cycle before putting the radio into active service — this brings the cell to 4.2V and gives the BMS adequate headroom to absorb the PTT transient.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBar indicator showing one fewer bar than expected after fitting this pack\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe THR9 uses a voltage-threshold bar indicator — each bar corresponds to a voltage band, not a fuel gauge reading. A new cell at storage voltage reads in the lower bands immediately after insertion, which looks like a low or degraded battery. This is not a fault with the pack. Place it on charge until the dock shows a full charge indication, then reinsert — the indicator will reflect the correct voltage and display the expected bar count.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43426313470042,"sku":"BWCS-ETH900TW-1","price":42.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43426313502810,"sku":"BWCS-ETH900TW-2","price":49.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43426313535578,"sku":"BWCS-ETH900TW-3","price":54.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-ETH900TW-1.webp?v=1779930633","url":"https:\/\/batteryweb.com\/products\/tetra-cassidian-thr9-replacement-battery-37v-2300mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}