General description Digital display with power supply, detachable, no welding required, and equipped with anti-reverse connection protection. This battery box can charge 21 flat head 18650 batteries and can function as a power bank when the built-in battery is used. The normal version requires a charging cable, while the version without a cable allows for quick charging. This DIY mobile power kit is designed for those with larger charging needs, featuring three types of charging interfaces: Micro, USB, and Type-C. Technical specifications Model: T21 Series with Light Battery type: 18650 x 21 flat head batteries (free welding) Size: Thickness 62mm, Width 84mm, Length 170mm Inner dimensions (without spring): Thickness 55mm, Width 74mm, Length 129mm Maximum power output/input: 5V-2.1A Color: Black Material: ABS Usage Monitor the power display to know the remaining battery life. Use only flat head batteries; pointed batteries are not compatible. Ensure correct placement of positive and