Efest SLIM K4 Type-C USB LED Battery Charger

Charge your rechargeable batteries faster and smarter with the Efest SLIM K4 Type-C USB Battery Charger. Designed for modern convenience, this intelligent 4-bay charger features a USB Type-C power input, automatic charging current adjustment, and advanced safety protections to provide dependable charging for a wide variety of lithium-ion batteries.

Whether you're charging 18650, 20700, 21700, or other compatible battery sizes, the SLIM K4 delivers efficient performance in a compact, travel-friendly design backed by a three-year manufacturer warranty.

Note: Batteries are not included.

Intelligent 4-Bay Charging

The Efest SLIM K4 independently monitors each charging slot, automatically selecting the appropriate charging current based on the number and type of batteries installed.

Automatic Charging Modes:

• 1 × Battery: 1.0A
• 2 × Batteries: 2 × 1.0A
• 3 × Batteries: 3 × 0.5A
• 4 × Batteries: 4 × 0.5A

This intelligent charging system helps maximize battery performance while promoting long battery life.

Modern USB Type-C Power Input

Unlike traditional chargers, the SLIM K4 features a USB Type-C input, providing fast, reliable, and convenient power delivery.

USB-C Benefits:

• Faster Charging Performance
• Stable Power Delivery
• Convenient USB Compatibility
• Ideal for Home or Travel

Power the charger using compatible USB power adapters or other approved USB power sources.

Easy-to-Read LED Indicators

Built-in LED lights provide real-time charging updates, making battery management simple and convenient.

LED Features:

• Charging Status Indicators
• Easy Battery Monitoring
• Automatic Charge Completion Display

Know exactly when your batteries are fully charged at a glance.

Advanced Safety Protection

The SLIM K4 is equipped with intelligent safety systems designed to protect both your batteries and charger during every charging cycle.

Safety Features:

• Reverse Polarity Protection
• Automatic Charge Completion
• Overcharge Prevention
• Intelligent Battery Monitoring

These protections help promote safe charging while extending battery lifespan.

Broad Battery Compatibility

The Efest SLIM K4 supports many of today's most commonly used rechargeable lithium-ion battery sizes.

Compatible Battery Sizes:

• 10440
• 14500
• 16340
• 17340
• 18350
• 18490
• 18500
• 18650
• 20700
• 21700
• 26500
• 26650

Compatible with 3.6V and 3.7V lithium-ion batteries.

Technical Specifications

• Input:
  • AC 100–240V, 50/60Hz
  • DC 5V / 2A
• Output Voltage: 4.2V ±0.05V
• Battery Cut-Off Voltage: 4.20V ±0.05V
• Auto Recharge Voltage: 4.10V ±0.10V
• USB Type-C Power Input
• Four Independent Charging Bays

Compact & Travel-Friendly

The slim, lightweight design makes the SLIM K4 easy to carry while providing dependable charging performance at home, in the office, or on the go.

Why You'll Love It:

• Compact Design
• USB Type-C Convenience
• Intelligent Charging
• Easy LED Monitoring
• Reliable Everyday Performance

What's Included

• 1 × Efest SLIM K4 LED Battery Charger
• 1 × USB Cable
• 1 × User Manual
• 1 × Warranty Card
• 1 × Scratch-Off Validation Serial Number

Battery Safety Guidelines

For safe charging and maximum battery life:

• Never charge damaged batteries.
• Inspect battery wraps before every charge.
• Do not overcharge or over-discharge rechargeable batteries.
• Always charge batteries on a clean, fire-resistant surface.
• Never leave charging batteries unattended.
• Store and transport batteries in protective, non-conductive battery cases.
• Dispose of batteries according to local recycling regulations.

Why Choose the Efest SLIM K4?

• Intelligent 4-Bay Charging
• USB Type-C Power Input
• Automatic Charging Current Selection
• LED Charging Indicators
• Reverse Polarity Protection
• Automatic Charge Completion
• Supports 18650, 20700 & 21700 Batteries
• Compact, Travel-Friendly Design
• Three-Year Manufacturer Warranty

The Efest SLIM K4 Type-C USB Battery Charger offers a modern, efficient charging solution for rechargeable lithium-ion batteries. With intelligent charging technology, broad battery compatibility, advanced safety protections, and convenient USB-C connectivity, it's an excellent choice for users seeking dependable everyday battery charging.