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Efest K4 Slim USB-C Battery Charger

  • $19.69
  • Ex Tax: $19.69
  • Product Code: M00002546
  • Availability: In Stock

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The Efest K4 Slim provides fast USB-C charging for up to four battery cells, and is compatible with a wide range of battery sizes.


Compatible with Lithium IMR 3.6V/3.7V Batteries:
10440 | 14500 | 16340 | 17340
18650 | 18490 | 18500 | 18650
26500 | 26650 | 20700 | 21700


The Slim K4 will automatically charge your battery cells a few seconds after they are installed. The indicator shows blue when in standby mode or the batteries are fully charged. The indicator will show white when the battery cells are charging.


Auto-detect charging current: 1 x 1.0A / 2 x 1.0A / 3 x 0.5A / 4 x 0.5A
Safe charging mode: CC & CV | Safe and convenient USB charger (5V 2A)
Monitors and charges each slot independently | Low voltage smart activation recovery function
Super lightweight and portable


The piano wire made spring ensures smooth gliding of each slot when installing and removing batteries. To achieve a more accurate charging voltage, the Slim K4 is designed with a steel cathode, with low resistance and hard chromium plating.

USB Port Design

Type-C USB helps to reduce the heat of the port effectively.

Six Protections

The built-in intelligent chip comes with six protections.
Short circuit protection | Automatic overcharging protection
Automatic over-discharge protection | Reverse polarity protection
0V activation recovery function | Hardware and software double protection.


Global insurance technical support with FCC, CE, RoHS certification


Please see our comprehensive guide to battery safety.

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