Efest Slim K4 four-bay charger with its box, charging cable and warranty card

Efest Slim K4 charger from the front, with four empty bays

Efest Slim K4 charger from the side, with a label and barcode sticker

Efest Slim K4 charger with its USB-C port and the charging cable on top

Efest Slim K4 USB C Charger

Name: Vape Society Supply
Price range: $$

Brand: Efest

Original price was: $24.99.Current price is: $14.99.

The Efest Slim K4 USB C Charger is a four-bay USB-C charger for 3.6V and 3.7V Li-ion and IMR batteries, including 21700s. It charges at 1A each for one or two batteries, or 0.5A each for three or four.

In stock

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Description

Efest Slim K4 USB C Charger Review

The Efest Slim K4 USB C Charger is a four-bay USB-C charger for 3.6V and 3.7V Li-ion and IMR batteries, including 18650s and 21700s. It charges one or two batteries at 1A each, or three or four at 0.5A each, from a 5V 2A USB adapter. See more from Efest or browse all battery chargers.

Slim K4 Highlights

Automatic Current

It sets the current by how many batteries are in: 1A each for one or two, and 0.5A each for three or four.

USB-C Input

It runs from a 5V 2A USB adapter through its USB-C port, and the cable comes in the box.

LED Indicators

Each bay’s LED indicator shows white while the battery charges and turns blue when it’s full.

Built-In Protection

Efest lists short-circuit and reverse polarity protection, automatic over-charge and over-discharge protection and 0V activation recovery.

Slim K4 Specs

Charging

Bays: 4
Batteries: 3.6V and 3.7V Li-ion and IMR
Charge voltage: 4.2V
Charge current: 1A each for one or two batteries, 0.5A each for three or four
Charging mode: CC and CV

Battery Sizes

Li-ion, IMR: 12 sizes from 10440 to 26650, such as 14500, 16340, 18350, 18650, 20700, 21700 and 26650

K4 Charger

Input: USB-C, 5V 2A
Display: one LED indicator per bay: white while charging, blue when full
Protection: short circuit, reverse polarity, over-charge and over-discharge, with 0V activation recovery
Size: 117 × 107 × 29mm
Body: fire-retardant ABS

Slim K4 Charge Current

Efest gives these currents:

Batteries charging	Current per battery
1	1A
2	1A each
3	0.5A each
4	0.5A each

Batteries

Charge only rechargeable 3.6V or 3.7V Li-ion and IMR batteries, never NiMH, alkaline or other single-use cells, and don’t leave the charger unattended while it’s plugged in.

How to Use the Slim K4

Plug it in: connect the USB-C cable from the box to the charger and a 5V 2A USB adapter.
Load the batteries: insert each battery with its ends matching the + and − marks. Efest says charging starts on its own within a few seconds.
Watch the lights: each bay’s light shows white while it charges and turns blue when the battery is full.

Who the Slim K4 Is For

It suits vapers who charge up to four 18650 or 21700 batteries from a USB adapter. For two bays, see the Slim K2, or for a screen and 2A charging, the LUC V4 Elite.

Good to know: No wall adapter comes in the box. Efest rates the input at 5V 2A, so use an adapter that supplies 2A.

What’s in the Slim K4 Box

Efest Slim K4 charger
USB-C charging cable
User manual and warranty card

FAQ

Efest Slim K4 FAQ

Does it charge 21700 batteries?

Yes. Efest lists 21700 and 20700 batteries, along with 18650s and 26650s. We sell IMREN 21700 batteries in 2-packs.

How fast does it charge?

1A per battery with one or two in, and 0.5A per battery with three or four in.

Does it come with a wall adapter?

No. It comes with a USB-C cable. Use a USB adapter rated for 5V 2A.

What do the lights mean?

White means the battery is charging. Blue means it’s full, or the bay is on standby.

Can it charge AA or NiMH batteries?

No. Efest lists 3.6V and 3.7V lithium batteries only.

How is it different from the Slim K2?

The Slim K2 has two bays and charges both batteries at 1A each. The K4 has four bays and drops to 0.5A each with three or four batteries in.