{"product_id":"lego®-spike™-battery-charger-fm4256","title":"LEGO® SPIKE™ Battery Charger (FM4256)","description":"\u003ch2\u003eFree Your Hub - Charge Batteries Independently\u003c\/h2\u003e\n\u003cp\u003eA DIY USB charger designed for LEGO® SPIKE™ Prime batteries, allowing you to charge robot batteries independently without tying up your SPIKE hub.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch2\u003e⚡ Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eDirect USB Charging: Charge using any 5V\/2A USB adapter\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eIndependent Operation: No need to connect to SPIKE hub\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eSmart LED Indicators: Visual charging status display\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eSafety Protection: Overcharge, overcurrent, short-circuit, and temperature protection\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eDIY Friendly: Simple 2-layer PCB design, easy to manufacture\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eEasy to Use: Uses FM4256 charging module with 3D-printed enclosure\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e📊 Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Voltage\u003c\/td\u003e\n\u003ctd\u003e5V DC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Current\u003c\/td\u003e\n\u003ctd\u003e2A (recommended)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCharging Current\u003c\/td\u003e\n\u003ctd\u003e1.2A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible Battery\u003c\/td\u003e\n\u003ctd\u003eSPIKE™ Prime 7.4V Li-ion (45610)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePCB Layers\u003c\/td\u003e\n\u003ctd\u003e2-layer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCharging Efficiency\u003c\/td\u003e\n\u003ctd\u003e94%\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003chr\u003e\n\u003ch2\u003e🔬 Technical Background: Why FM4256?\u003c\/h2\u003e\n\u003cp\u003eThe SPIKE Prime Hub internally uses the \u003cstrong\u003eMPS MP2639A\u003c\/strong\u003e charging IC. After reverse engineering research, we selected \u003cstrong\u003eFM4256\u003c\/strong\u003e for this standalone charger because it has nearly identical electrical specifications:\u003c\/p\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eMP2639A (in SPIKE Hub)\u003c\/th\u003e\n\u003cth\u003eFM4256 (This Project)\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Voltage\u003c\/td\u003e\n\u003ctd\u003e5V\u003c\/td\u003e\n\u003ctd\u003e5V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOutput Voltage\u003c\/td\u003e\n\u003ctd\u003e8.4V\u003c\/td\u003e\n\u003ctd\u003e8.4V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTopology\u003c\/td\u003e\n\u003ctd\u003eBoost Switching\u003c\/td\u003e\n\u003ctd\u003eSynchronous Boost\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCharging Method\u003c\/td\u003e\n\u003ctd\u003eCC\/CV\u003c\/td\u003e\n\u003ctd\u003eCC\/CV\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBattery Type\u003c\/td\u003e\n\u003ctd\u003e2S Li-ion\u003c\/td\u003e\n\u003ctd\u003e2S Li-ion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eKey Differences\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eMP2639A has bidirectional operation (charge\/discharge) → Not needed for standalone charger\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eMP2639A has MID pin for cell balancing → \u003cstrong\u003eSPIKE battery seems not use this feature\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eFM4256 is more cost-effective and easier to source\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003eAbout SPIKE Battery's 3 Pins\u003c\/h2\u003e\n\u003cp\u003eResearch findings reveal the 3-pin configuration:\u003c\/p\u003e\n\u003cpre\u003e\u003ccode class=\"language-text\"\u003ePin 1 (Left)   —— BAT+ (Battery Positive, 7.3-8.4V)\nPin 2 (Middle) —— NTC (Temperature Sensor, 10kΩ @ 25°C)(Seems)\nPin 3 (Right)  —— BAT- (Battery Negative, GND)\n\u003c\/code\u003e\u003c\/pre\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003ePin 2 is an NTC thermistor\u003c\/strong\u003e, used for temperature protection during charging (0°C ~ 50°C)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eNot a cell balancing pin\u003c\/strong\u003e (MID), SPIKE battery doesn't expose cell midpoint\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eFM4256 module may not have NTC input, but this doesn't affect basic charging functionality\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eBattery has internal protection board, safe for normal indoor use\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eConclusion\u003c\/h3\u003e\n\u003cp\u003eFM4256 provides all necessary charging functions and is ideal for this DIY project.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch2\u003e🛠️ Hardware Design\u003c\/h2\u003e\n\u003ch3\u003eMain Components\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eFM4256 Charging Module\u003c\/strong\u003e: 2S Li-ion battery USB boost charging IC\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e3-Pin Connector\u003c\/strong\u003e: Connects to SPIKE battery\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003e3D-Printed Enclosure\u003c\/strong\u003e: Uses M3 screws for case\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSPIKE Prime Hub Battery (45610)\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eType: 2S Lithium-ion battery\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eCapacity: 2100mAh\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eNominal Voltage: 7.3-7.4V\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eCharging Voltage: 8.3-8.4V\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e🚨 LED Status Indicators (FM4256 S22)\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eStatus\u003c\/th\u003e\n\u003cth\u003eLED1 (Blue)\u003c\/th\u003e\n\u003cth\u003eLED2 (Red)\u003c\/th\u003e\n\u003cth\u003eDescription\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eStandby\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eBlinking\u003c\/td\u003e\n\u003ctd\u003eON\u003c\/td\u003e\n\u003ctd\u003eNo battery connected\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eCharging\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eOFF\u003c\/td\u003e\n\u003ctd\u003eON\u003c\/td\u003e\n\u003ctd\u003eBattery charging in progress\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003eComplete\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003eON\u003c\/td\u003e\n\u003ctd\u003eOFF\u003c\/td\u003e\n\u003ctd\u003eCharging complete, ready to remove\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eNote\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eSome modules only show Red LED on first power-up\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eLED behavior normalizes after inserting and removing battery once\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eIC models S21 and S22 have different LED patterns; most are S22\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e📖 Usage Instructions\u003c\/h2\u003e\n\u003ch3\u003ePreparation\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cp\u003eConnect \u003cstrong\u003e5V\/2A\u003c\/strong\u003e USB power adapter\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eInsert SPIKE Prime battery into connector\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eEnsure correct battery orientation (guided by 3D frame to prevent reverse connection)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003ch3\u003eCharging Process\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cp\u003eBlue LED blinking, red LED on → Standby mode\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eAfter connecting battery → Blue LED off, red LED on → Charging\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eCharging complete → Blue LED on, red LED off\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eRemove battery\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003ch3\u003eImportant Notes\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eCharging time: ~0.5-1.5 hours (depending on remaining battery capacity)\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eMonitor during charging, do not leave unattended\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eRemove battery when fully charged, do not leave on charger for extended periods\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eDo not use continuously for more than 24 hours\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e⚠️ Safety Warnings\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eFor LEGO® SPIKE™ Prime \/ RI battery only\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eUse 5V \/ 2A USB charger\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eDo not reverse polarity or short terminals\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eCharge under adult supervision\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eKeep ventilated – do not cover\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eStop use if heat, smoke, or odor occurs\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eAvoid charging in extreme temperatures (\u0026lt;5°C or \u0026gt;40°C)\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eSafe for normal indoor use\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e⚠️ Disclaimer\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eDIY \/ prototype – no testing or certification\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eNo BMS or balancing included\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eMisuse may cause fire, explosion, or injury\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eFor educational\/technical use under adult guidance\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eUser assumes all risks and responsibility for use\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eProvided \"AS IS\" without warranty or liability\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eManufacturer not liable for any loss, damage or injury\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e📚 Resources \u0026amp; References\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eFM4256 Datasheet\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eSPIKE Prime Battery Specifications\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eSPIKE Prime Hub Reverse Engineering\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eLi-ion Battery Charging Best Practices\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003chr\u003e\n\u003ch2\u003e📝 Legal Notice\u003c\/h2\u003e\n\u003cp\u003eLEGO® is a trademark of the LEGO Group which does not sponsor, authorize or endorse this project.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch2\u003e📄 License | 授權協議\u003c\/h2\u003e\n\u003cp\u003eThis project is open source and available under the \u003cstrong\u003eBSD-3-Clause license\u003c\/strong\u003e.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch2\u003e🤝 Contributing | 貢獻\u003c\/h2\u003e\n\u003cp\u003eContributions, issues, and feature requests are welcome!\u003c\/p\u003e\n\u003cp\u003e⚠️ \u003cstrong\u003eUse at your own risk - Please understand Li-ion battery charging safety\u003c\/strong\u003e\u003c\/p\u003e","brand":"AXIONE","offers":[{"title":"Default Title","offer_id":44658963578963,"sku":null,"price":39.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0716\/5257\/3267\/files\/LEGO_SPIKE_BatteryCharger_FM4256.png?v=1779783704","url":"https:\/\/wzmvad-mf.myshopify.com\/products\/lego%c2%ae-spike%e2%84%a2-battery-charger-fm4256","provider":"AXIONE","version":"1.0","type":"link"}