4slot rechargeable 18650 battery case enables solder powerbank assembly, featuring swappable flat battery slots for easy maintenance and capacity upgrades Durable ABS construction securely houses unprotected flat 18650 batteries (not included) in precise alignment for electrical contact and performance Compact powerbank shell reliably charges smartphones and tablets during outdoor activities, business trips, or power outages Ideal for enthusiasts and DIYers seeking a , userserviceable portable charging solution Use scenarios Outdoor adventures such as hiking or camping: assemble a capacity powerbank with interchangeable cells to keep devices charged for navigation, communications, or emergency signaling Remote work or travel: swap in fresh cells on the go to maintain reliable charging for phones, tablets, and other USBpowered devices without soldering Home or office power outages: deploy a readytouse, expandable charging solution to keep essential devices powered during an outage