Klarus K1 Charger
(6 reviews)
The Klarus K1 charges your Li-ion cells and NiMH or NiCd batteries over USB from a single bay, with a clear LED indicator you can trust.
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Characteristics
- Compatibility: Li-ion 10440 to 26650 + NiMH/NiCd AA to C
- Charging: USB, 0.5A or 1A selectable
- Indicator: LED charge and end-of-charge light
- Format: Single bay, 115 x 37 x 28 mm, about 45g
- Compact, versatile: Li-ion, LiFePO4 and NiMH on 1 bay
Detailed overview: Klarus K1 battery charger
The Klarus K1 is a single-bay USB charger designed for flashlight users, camera owners and anyone with gear that runs on interchangeable cells. Its promise: one small unit able to charge almost every common cell and battery format, so you don't need a different charger for every device.
On compatibility, it covers a wide range of Li-ion and LiFePO4 cells, from the tiny 10440 up to the 26650, including the common 14500, 16340 (RCR123A), 17500, 17670, 18350, 18490, 18650 and 22650 sizes. It also accepts NiMH and NiCd batteries in AA, AAA, AAAA and C sizes, making it a versatile companion for anyone with several devices running on rechargeable cells.
Operation stays simple: a single button lets you select the chemistry of the inserted cell and the charging current, 0.5A or 1A, while an LED indicator shows charging progress and then confirms when charging is complete. The charger automatically cuts power once charging finishes, to prevent overcharging, and includes reverse-polarity and short-circuit protection. A reactivation function can even bring back Li-ion cells that dropped to zero volts, as long as they aren't permanently damaged.
Powered by a simple USB cable (included, non-magnetic) plugged into the mains, a computer or a car charger, the K1 slips easily into a pouch or bag thanks to its compact size of roughly 115 x 37 x 28 mm and a weight of around 40 grams. Its fire-retardant ABS shell and heat-dissipation design make it a sturdy backup charger built for travel.
This early Klarus model has since been replaced in the official lineup by the K1 Pro, which adds USB-C and charging up to 2A. The original K1 remains available through some retailers, and it still makes sense for anyone after a simple, compact, widely compatible single-bay charger at an accessible price.
Full specifications
Detailed characteristics
Charging capacity
| Number of slots?Number of batteries that can be charged at the same time. | 1 |
|---|---|
| Compatible formats?Accepted battery formats (AA, AAA, 18650, 21700...). | 10440, 14500, 16340, 17500, 17670, 18350, 18490, 18650, 22650, 26650 |
| Compatible chemistries?Recognised battery chemistries (Li-ion, LiFePO4, NiMH, NiCd...). | Li-ion, LiFePO4, NiMH, NiCd |
| Max charging current?Maximum charging current per slot, in milliamps. | 1000 mA |
| Adjustable charging current?The user can manually pick the charging current. | Yes |
Power input
| Power source?Built-in mains plug, USB port (Micro-USB or USB-C) or 12 V car socket. | Micro-USB |
|---|
Output and features
| USB output (device charging)?The charger can also act as a power bank: it uses the inserted cells to charge another device. | No |
|---|
Display and diagnostics
| Display?Type of visual feedback on charging status. | LED per slot |
|---|---|
| Automatic chemistry detection?The charger automatically adapts its charging profile to the inserted cell, with no manual setting. | Yes |
| Test / repair functions?Advanced functions beyond plain charging: real capacity measurement, internal resistance, reconditioning of worn cells, discharge cycles. | Reconditioning / revival |
Size
| Weight?Weight of the empty charger, in grams. | 45 g |
|---|---|
| Dimensions (L × W × H)?Length × width × height, in millimetres. | 115 × 37 × 32 mm |
Related video
Video: Klarus K1 USB Smart Battery Charger - Review - Published on 25/01/2017
Our tester's review: Christophe Delpuech
This little Klarus K1 has lived in our cell pouch for a while, pulled out to rescue a flashlight or top up a tired 18650 before a trip. Its main strength: it swallows almost anything, from the tiny 10440 up to a full-size 26650, plus NiMH AA and AAA cells, so you don't need a drawer full of chargers. The current-select button (0.5A or 1A) and the LED indicator keep things simple. Its reactivation function for Li-ion cells that dropped to zero volts even saved a battery we'd written off as dead. Two honest downsides: 1A is modest for a large cell, expect several hours for a full charge, and Klarus has since replaced this model with the K1 Pro (USB-C, 2A). Still, as a compact, versatile backup charger at this price, it remains a safe bet.
Frequently asked questions: Klarus K1 battery charger
Li-ion and LiFePO4 cells from 10440 to 26650 (14500, 16340/RCR123A, 18490, 18650, 22650...) plus NiMH and NiCd batteries in AA, AAA, AAAA and C sizes. The chemistry is selected manually with the dedicated button.
Two settings, 0.5A or 1A, chosen with the same button used for chemistry selection. With a standard 5V/1A USB source, expect several hours for a full charge of a large cell like a 26650.
No, this model has been discontinued from the official Klarus lineup and replaced by the K1 Pro (USB-C, up to 2A). The original K1 remains available through some retailers, including Amazon, while stocks last.
No, the Klarus K1 has only one bay. To charge several cells at the same time, look at a 2 or 4-bay model such as the Klarus K2.
It isn't recommended: a Li-ion 18650 cell needs controlled voltage and current to charge safely. A charger like the K1 handles that precision automatically, unlike an improvised charge.
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Published on 01/09/2026