Efest Slim K1 Battery Charger

Efest Slim K1 Battery Charger – Compact Single-Slot Charging with Essential Safety Features

The Efest Slim K1 Battery Charger is a highly portable, cost-effective solution for charging a single lithium-ion battery. Designed for users who need a simple, safe, and reliable charger for their everyday vaping or electronic devices, the Slim K1 combines intelligent charging circuitry with essential safety protections in a slim, durable housing.

Broad Battery Compatibility in a Single Slot

Despite its compact size, the Slim K1 supports a wide variety of 3.6V/3.7V lithium-ion batteries, making it compatible with most vaping and flashlight cells. Its spring-loaded piano-wire slot ensures a secure fit across different battery lengths and diameters.

Compatible sizes include:
10440, 14500, 14650, 16340, 16650, 17650, 17670, 18350, 18490, 18500, 18650, 20700, 21700, and 26650.

This flexibility allows users to charge a wide range of battery types without the need for multiple chargers.

Smart Charging with Micro USB Convenience

The Slim K1 uses a Micro USB input, drawing DC 5V / 1A from standard USB ports, wall adapters, or power banks. The charger outputs a constant 1A charge current, making it ideal for single battery charging without overheating or overloading the cell.

Key Charging Parameters

• 1A Constant Current (CC): 1000mA ±10% for efficient, stable charging

• Auto Cut-Off Voltage: 4.20V ±0.05V to prevent overcharging

• CV Cut-Off Current: Less than 100mA to ensure the battery finishes charging safely

• Auto Recharge: Resumes charging if the battery voltage drops to 4.10V ±0.10V during rest periods

• Activation Current: 50mA – 100mA, designed to safely wake deeply discharged batteries

Integrated Safety Protections

The Slim K1 incorporates multiple layers of protection:

• Reverse Polarity Protection: Safeguards against incorrect battery insertion

• Short Circuit Protection: Prevents device damage from electrical faults

• Overcharge Protection: Automatically cuts off charging at full capacity

• Temperature Range Compliance: Operates safely between 0°C and 40°C, stores safely from -40°C to 70°C

These features ensure consistent, reliable charging across various environments and battery types.

LED Charge Status Indicator

A single LED indicator provides clear feedback:

• Red: Charging

• Green: Fully charged / No battery inserted

This simple interface makes operation intuitive, even for first-time users.

Technical Specifications

Recommended Usage

The Efest Slim K1 is best suited for:

• Vapers charging single 18650, 20700, or 21700 cells for regulated mods or pod systems

• Flashlight enthusiasts or DIY hobbyists needing a compact, travel-ready charger

• Anyone requiring single-slot charging without complex settings

Practical Everyday Performance

With its single-slot design, USB power input, and essential safety protections, the Slim K1 is a convenient solution for those who only need to charge one battery at a time. Its compact footprint makes it easy to pack in a travel kit, while its reliable charging profile ensures battery safety and longevity.

Final Thoughts

The Efest Slim K1 Battery Charger offers a practical balance of affordability, portability, and safety. For users who want a no-nonsense single-slot charger to maintain their vaping or flashlight batteries, the Slim K1 delivers essential features in a compact package.