{"product_id":"5s-21v-30a-45a-bms-lithium-battery-protection-board-with-ntc","title":"5S 21V 30A\/45A BMS Lithium Battery Protection Board with NTC","description":"\u003ch2\u003e5S 18V–21V 30A\/45A BMS Lithium Battery Charging Protection Board with NTC \u0026amp; Balance\u003c\/h2\u003e\n\u003cp\u003eProtect and extend the life of your lithium battery packs with this high-performance \u003cstrong\u003e5S BMS (Battery Management System) Protection Board\u003c\/strong\u003e. Designed for 18V–21V lithium-ion cell configurations, this module delivers reliable overcharge, over-discharge, and overcurrent protection — all in a compact SMD package. Available in 30A and 45A current ratings and sold in packs of 1, 2, or 3 boards.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003e5-Series Cell Configuration:\u003c\/strong\u003e Supports 18V–21V (5S) lithium-ion battery packs for power tools, e-bikes, and DIY energy storage projects.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDual Current Options:\u003c\/strong\u003e Choose between 30A and 45A continuous discharge ratings to match your specific load requirements.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNTC Resistor Temperature Protection:\u003c\/strong\u003e Built-in NTC thermistor monitors battery temperature and automatically cuts off current when the board exceeds safe operating limits (0–80°C), preventing thermal runaway.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eActive Cell Balancing:\u003c\/strong\u003e Equalizes voltage across all 5 cells during charging, maximising total capacity and prolonging overall pack lifespan.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOvercharge \u0026amp; Over-Discharge Protection:\u003c\/strong\u003e Automatically disconnects the circuit when any individual cell reaches its upper or lower voltage threshold.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOvercurrent \u0026amp; Short-Circuit Protection:\u003c\/strong\u003e Instantaneous cut-off on load short-circuit events, safeguarding both the board and your battery cells.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSMD Module Design:\u003c\/strong\u003e Compact surface-mount board is easy to integrate into battery enclosures, power tool packs, and custom battery builds.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSupply Voltage:\u003c\/strong\u003e 21V (5S fully charged state)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOperating Temperature:\u003c\/strong\u003e 0–80°C\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePackage Options:\u003c\/strong\u003e 1 PC, 2 PCS, or 3 PCS — stock up and save.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eIdeal Applications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e18V–21V cordless power tools (drills, saws, grinders)\u003c\/li\u003e\n  \u003cli\u003eDIY lithium battery pack builds and replacements\u003c\/li\u003e\n  \u003cli\u003eE-bike and electric scooter battery management\u003c\/li\u003e\n  \u003cli\u003ePortable power stations and energy storage systems\u003c\/li\u003e\n  \u003cli\u003eRC vehicles and robotics power packs\u003c\/li\u003e\n  \u003cli\u003eComputer and electronics backup power modules\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003ctable\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCell Configuration\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e5S (5 Series)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eNominal Voltage\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e18V (charged: 21V)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eContinuous Current\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e30A \/ 45A (selectable)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eTemperature Sensor\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eNTC Resistor (built-in)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eOperating Temperature\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e0°C – 80°C\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003ePackage Type\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eSMD Module\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCondition\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eNew\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCountry of Origin\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eMade in Mainland China\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eRelated Products You May Like\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/electromagnetic-induction-tester-coil-motherboard-fault-detector\"\u003eElectromagnetic Induction Tester – Coil \u0026amp; Circuit Fault Detector\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/air-compressor-pressure-gauge-0-10-0-12-0-25-bar-hydraulic-diy\"\u003eAir Compressor Pressure Gauge 0-10\/0-12\/0-25 Bar | DIY Tool\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/360-bicycle-chain-cleaner-tool-gear-cleaning-kit\"\u003e360° Bicycle Chain Cleaner Tool | Bike Gear Cleaning Kit\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eLearn more: \u003ca href=\"https:\/\/www.energystar.gov\/products\" target=\"_blank\" rel=\"noopener\"\u003eENERGY STAR product efficiency guidance\u003c\/a\u003e\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003ch4\u003eQ: What does the NTC resistor do on this BMS protection board?\u003c\/h4\u003e\n\u003cp\u003eA: The NTC (Negative Temperature Coefficient) resistor is a built-in thermistor that continuously monitors the temperature of the BMS board and battery cells. When the temperature rises beyond the safe threshold, the BMS automatically disconnects the circuit to prevent overheating and potential thermal runaway, keeping your battery pack safe during heavy use or charging.\u003c\/p\u003e\n\u003ch4\u003eQ: What is the difference between the 30A and 45A versions of this BMS board?\u003c\/h4\u003e\n\u003cp\u003eA: The ampere rating refers to the maximum continuous discharge current the board can safely handle. The 30A version suits lighter loads such as smaller power tools or moderate-draw electronics, while the 45A version is designed for higher-demand applications like heavy-duty cordless tools, e-bikes, or high-current DIY battery packs. Choose based on the peak current draw of your specific device.\u003c\/p\u003e\n\u003ch4\u003eQ: Can this BMS board be used to replace an existing battery protection board in a cordless power tool?\u003c\/h4\u003e\n\u003cp\u003eA: Yes — this 5S BMS module is widely compatible with 18V–21V lithium-ion battery packs commonly found in cordless drills, circular saws, and grinders. Always verify your existing pack's cell count (5S), voltage, and current requirements before installing to ensure compatibility.\u003c\/p\u003e\n\u003ch4\u003eQ: Is the cell balancing feature active during charging only, or also during discharge?\u003c\/h4\u003e\n\u003cp\u003eA: The balancing function on this BMS board is primarily active during the charging cycle. It equalises the voltage across all five cells as they charge, ensuring each cell reaches the same state of charge and preventing individual cells from being overcharged or undercharged — which significantly extends the overall lifespan of your battery pack.\u003c\/p\u003e\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"What does the NTC resistor do on this BMS protection board?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"The NTC (Negative Temperature Coefficient) resistor is a built-in thermistor that continuously monitors the temperature of the BMS board and battery cells. 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It equalises the voltage across all five cells as they charge, ensuring each cell reaches the same state of charge and preventing individual cells from being overcharged or undercharged — which significantly extends the overall lifespan of your battery pack.\"}}]}\u003c\/script\u003e\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\": \"https:\/\/schema.org\", \"@type\": \"BreadcrumbList\", \"itemListElement\": [{\"@type\": \"ListItem\", \"position\": 1, \"name\": \"Home\", \"item\": \"https:\/\/n8ande-60.myshopify.com\/\"}, {\"@type\": \"ListItem\", \"position\": 2, \"name\": \"Home page\", \"item\": \"https:\/\/n8ande-60.myshopify.com\/collections\/frontpage\"}, {\"@type\": \"ListItem\", \"position\": 3, \"name\": \"5S 21V 30A\/45A BMS Lithium Battery Protection Board with NTC\", \"item\": \"https:\/\/n8ande-60.myshopify.com\/products\/5s-18v-21v-bms-lithium-battery-protection-board-ntc-balance\"}]}\u003c\/script\u003e","brand":"Axl","offers":[{"title":"3PCS","offer_id":43692649709629,"sku":"3:18247432443#3PCS","price":50.42,"currency_code":"USD","in_stock":true},{"title":"2PCS","offer_id":43692649742397,"sku":"3:1981284404#2PCS","price":29.34,"currency_code":"USD","in_stock":true},{"title":"1PC","offer_id":43692649775165,"sku":"3:201010228#1PC","price":16.66,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0671\/3439\/0333\/files\/S945b58293e2542b6be52ddb0bad2a84bT.webp?v=1790178016","url":"https:\/\/qtiply.com\/products\/5s-21v-30a-45a-bms-lithium-battery-protection-board-with-ntc","provider":"QTP","version":"1.0","type":"link"}