{"product_id":"21v-5s-bms-protection-board-18650-lithium-battery-pack-diy","title":"21V 5S Li-ion BMS Protection Board for 18650 Battery Pack DIY","description":"\n\u003ch2\u003e21V 5S Li-ion BMS Charging Protection Board for 18650 Lithium Battery Packs\u003c\/h2\u003e\n\u003cp\u003eBuild safer, longer-lasting DIY battery packs with this compact \u003cstrong\u003e21V 5-Series (5S) Battery Management System (BMS) \/ PCM Protection Board\u003c\/strong\u003e. Designed for 18650 lithium-ion and lithium polymer (LiPo) cell configurations, this module monitors and safeguards your battery pack automatically — giving you confidence in every build.\u003c\/p\u003e\n\n\u003ch3\u003eKey Protection Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOvercharge Protection\u003c\/strong\u003e – Prevents cells from being charged beyond safe voltage thresholds, extending overall pack lifespan.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eOver-Discharge Protection\u003c\/strong\u003e – Cuts off output before cells drop to damaging low-voltage levels.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eShort Circuit Protection\u003c\/strong\u003e – Instantly interrupts current flow in the event of a short, protecting your cells and connected devices.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBalanced Cell Management\u003c\/strong\u003e – Supports 5 series-connected lithium cells for a nominal 21V output, ideal for power tools, e-bikes, and DIY electronics.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eConfiguration:\u003c\/strong\u003e 5S (5 cells in series)\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCompatible Voltage:\u003c\/strong\u003e 21V Li-ion \/ LiPo battery packs\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCompatible Cells:\u003c\/strong\u003e 18650 lithium-ion and lithium alloy batteries\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePackage Contents:\u003c\/strong\u003e 1 × BMS\/PCM Protection Board\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSize:\u003c\/strong\u003e As shown in product images\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCountry of Origin:\u003c\/strong\u003e Made in China\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWho Is This For?\u003c\/h3\u003e\n\u003cp\u003eThis BMS board is perfect for electronics hobbyists, makers, and engineers building custom battery packs for power tools, RC vehicles, e-scooters, portable power stations, and other 21V DIY projects. Whether you're assembling from scratch or replacing a faulty protection circuit, this module is a reliable, cost-effective solution.\u003c\/p\u003e\n\n\u003ch3\u003eImportant Notes\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003eDue to manual measurement, please allow a tolerance of 1–3mm.\u003c\/li\u003e\n  \u003cli\u003eProduct color may vary slightly from images due to monitor differences — please refer to the actual item received.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eRelated Products You May Like\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/1-channel-scr-solid-state-relay-switch-module-dc3-24v-40a-optocoupler\"\u003e1-Channel SCR Solid State Relay Module DC3-24V 40A Optocoupler\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/10-pack-12v-3-pin-pc-fan-power-extension-cable-26cm-cpu-gpu-cooler\"\u003e10-Pack 12V 3-Pin PC Fan Extension Cable 26cm – CPU GPU Cooler\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor general guidance on lithium battery safety standards, visit the U.S. Consumer Product Safety Commission – Lithium Battery Safety.\u003c\/p\u003e\n\n\u003cp\u003eLearn more: \u003ca href=\"https:\/\/en.wikipedia.org\/wiki\/Battery_management_system\" target=\"_blank\" rel=\"noopener\"\u003eBattery management system\u003c\/a\u003e\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003ch4\u003eQ: What does a BMS (Battery Management System) protection board do for a 5S lithium battery pack?\u003c\/h4\u003e\n\u003cp\u003eA: A BMS protection board monitors and manages your battery pack's voltage, current, and temperature. For a 5S 21V lithium pack, it actively prevents overcharging, over-discharging, and short circuits — all of which can permanently damage cells or create hazards. It is an essential component for any safe DIY lithium battery build.\u003c\/p\u003e\n\u003ch4\u003eQ: Is this BMS board compatible with 18650 lithium-ion cells?\u003c\/h4\u003e\n\u003cp\u003eA: Yes. This 5S PCM\/BMS board is specifically designed for use with 18650 lithium-ion cells as well as lithium alloy (LiPo) cells arranged in a 5-series configuration, producing a nominal 21V output — commonly used in power tools and DIY electronics projects.\u003c\/p\u003e\n\u003ch4\u003eQ: How many cells does this 5S BMS board support?\u003c\/h4\u003e\n\u003cp\u003eA: This board supports 5 lithium cells connected in series (5S), resulting in a fully charged voltage of approximately 21V. It does not support parallel configurations on its own — additional hardware would be required for series-parallel (e.g., 5S2P) arrangements.\u003c\/p\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"What does a BMS (Battery Management System) protection board do for a 5S lithium battery pack?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"A BMS protection board monitors and manages your battery pack's voltage, current, and temperature. For a 5S 21V lithium pack, it actively prevents overcharging, over-discharging, and short circuits — all of which can permanently damage cells or create hazards. It is an essential component for any safe DIY lithium battery build.\"}}, {\"@type\": \"Question\", \"name\": \"Is this BMS board compatible with 18650 lithium-ion cells?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. This 5S PCM\/BMS board is specifically designed for use with 18650 lithium-ion cells as well as lithium alloy (LiPo) cells arranged in a 5-series configuration, producing a nominal 21V output — commonly used in power tools and DIY electronics projects.\"}}, {\"@type\": \"Question\", \"name\": \"How many cells does this 5S BMS board support?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"This board supports 5 lithium cells connected in series (5S), resulting in a fully charged voltage of approximately 21V. It does not support parallel configurations on its own — additional hardware would be required for series-parallel (e.g., 5S2P) arrangements.\"}}]}\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:\/\/oasis-select.com\/\"}, {\"@type\": \"ListItem\", \"position\": 2, \"name\": \"Electronics \u0026 Tech\", \"item\": \"https:\/\/oasis-select.com\/collections\/electronics-tech\"}, {\"@type\": \"ListItem\", \"position\": 3, \"name\": \"21V 5S Li-ion BMS Protection Board for 18650 Battery Pack DIY\", \"item\": \"https:\/\/oasis-select.com\/products\/21v-5s-bms-protection-board-18650-lithium-battery-pack-diy\"}]}\u003c\/script\u003e","brand":"Oasis Select","offers":[{"title":"green","offer_id":47727511306345,"sku":"14:200004889#green","price":6.2,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0679\/7931\/3257\/files\/Seae342358f9943418c59e351040400a1l.webp?v=1782662250","url":"https:\/\/oasis-select.com\/products\/21v-5s-bms-protection-board-18650-lithium-battery-pack-diy","provider":"Oasis Select","version":"1.0","type":"link"}